Maria M. Hornberger, MD

The Diagnosis: Dermatomyofibroma

Dermatomyofibroma is an uncommon, benign, cutaneous mesenchymal neoplasm composed of fibroblasts and myofibroblasts.^1-3 This skin tumor was first described in 1991 by Hugel⁴ in the German literature as plaquelike fibromatosis. Pediatric dermatomyofibromas are exceedingly rare, with pediatric patients ranging in age from infants to teenagers.¹

Clinically, dermatomyofibromas appear as long-standing, isolated, ill-demarcated, flesh-colored, slightly hyperpigmented or erythematous nodules or plaques that may be raised or indurated.¹ Dermatomyofibromas may present with constant mild pain or pruritus, though in most cases the lesions are asymptomatic.^1,3 The clinical presentation of dermatomyofibroma has a few distinct differences in children compared to adults. In adulthood, dermatomyofibroma has a strong female predominance and most commonly is located on the shoulder and adjacent upper body regions, including the axilla, neck, upper arm, and upper trunk.^1-3 In childhood, the majority of dermatomyofibromas occur in young boys and usually are located on the neck with other upper body regions occurring less frequently.^1,2 A shared characteristic includes the tendency for dermatomyofibromas to have an initial period of enlargement followed by stabilization or slow growth.¹ Reported pediatric lesions have ranged in size from 4 to 60 mm with an average size of 14.9 mm (median, 12 mm).²

The diagnosis of dermatomyofibroma is based on histopathologic features in addition to clinical presentation. Histology from punch biopsy usually reveals a noninvasive dermal proliferation of bland, uniform, slender spindle cells oriented parallel to the overlying epidermis with increased and fragmented elastic fibers.^1,3 Infiltration into the mid or deep dermis is common. The adnexal structures usually are spared; the stroma contains collagen and increased small blood vessels; and there typically is no inflammatory infiltrate, except for occasional scattered mast cells.² Cytologically, the monomorphic spindleshaped tumor cells have an ill-defined, pale, eosinophilic cytoplasm and nuclei that are elongated with tapered edges.³ Dermatomyofibroma has a variable immunohistochemical profile, as it may stain focally positive for CD34 or smooth muscle actin, with occasional staining of factor XIIIa, desmin, calponin, or vimentin.^1-3 Normal to increased levels of often fragmented elastic fibers is a helpful clue in distinguishing dermatomyofibroma from dermatofibroma, hypertrophic scar, dermatofibrosarcoma protuberans, and pilar leiomyoma, in which elastic fibers typically are reduced.³ Differential diagnoses of mesenchymal tumors in children include desmoid fibromatosis, connective tissue nevus, myofibromatosis, and smooth muscle hamartoma.¹

A punch biopsy with clinical observation and followup is recommended for the management of lesions in cosmetically sensitive areas or in very young children who may not tolerate surgery. In symptomatic or cosmetically unappealing cases of dermatomyofibroma, simple surgical excision remains a viable treatment option. Recurrence is uncommon, even if only partially excised, and no instances of metastasis have been reported.^1-5

Dermatomyofibromas may be mistaken for several other entities both benign and malignant. For example, the benign dermatofibroma is the second most common fibrohistiocytic tumor of the skin and presents as a firm, nontender, minimally elevated to dome-shaped papule that usually measures less than or equal to 1 cm in diameter with or without overlying skin changes.^5,6 It primarily is seen in adults with a slight female predominance and favors the lower extremities.⁵ Patients usually are asymptomatic but often report a history of local trauma at the lesion site.⁶ Histologically, dermatofibroma is characterized by a nodular dermal proliferation of spindleshaped fibrous cells and histiocytes in a storiform pattern (Figure 1).⁶ Epidermal induction with acanthosis overlying the tumor often is found with occasional basilar hyperpigmentation.⁵ Dermatofibroma also characteristically has trapped collagen (“collagen balls”) seen at the periphery.^5,6

Piloleiomyomas are benign smooth muscle tumors arising from arrector pili muscles that may be solitary or multiple.⁵ Clinically, they typically present as firm, reddish-brown to flesh-colored papules or nodules that develop more commonly in adulthood.^5,7 Piloleiomyomas favor the extremities and trunk, particularly the shoulder, and can be associated with spontaneous or induced pain. Histologically, piloleiomyomas are well circumscribed and centered within the reticular dermis situated closely to hair follicles (Figure 2).⁵ They are composed of numerous interlacing fascicles or whorls of smooth muscle cells with abundant eosinophilic cytoplasm and blunt-ended, cigar-shaped nuclei.^5,7

Solitary cutaneous myofibroma is a benign fibrous tumor found in adolescents and adults and is the counterpart to infantile myofibromatosis.⁸ Clinically, myofibromas typically present as painless, slow-growing, firm nodules with an occasional bluish hue. Histologically, solitary cutaneous myofibromas appear in a biphasic pattern, with hemangiopericytomatous components as well as spindle cells arranged in short bundles and fascicles resembling leiomyoma (Figure 3). The spindle cells also have abundant eosinophilic cytoplasm with short plump nuclei; the random, irregularly intersecting angles can be used to help differentiate myofibromas from smooth muscle lesions.⁸ Solitary cutaneous myofibroma is in the differential diagnosis for dermatomyofibroma because of their shared myofibroblastic nature.⁹

Dermatofibrosarcoma protuberans (DFSP) is an uncommon, locally invasive sarcoma with a high recurrence rate that favors young to middle-aged adults, with rare childhood onset reported.^5,10,11 Clinically, DFSP typically presents as an asymptomatic, slow-growing, firm, flesh-colored, indurated plaque that develops into a violaceous to reddish-brown nodule.⁵ The atrophic variant of DFSP is characterized by a nonprotuberant lesion and can be especially difficult to distinguish from other entities such as dermatomyofibroma.¹¹ The majority of DFSP lesions occur on the trunk, particularly in the shoulder or pelvic region.⁵ Histologically, early plaque lesions are comprised of monomorphic spindle cells arranged in long fascicles (parallel to the skin surface), infiltrating adnexal structures, and subcutaneous adipocytes in a multilayered honeycomb pattern; the spindle cells of late nodular lesions are arranged in short fascicles in a matted or storiform pattern (Figure 4).^5,10 Early stages of DFSP as well as variations in childhood-onset DFSP can easily be misdiagnosed and incompletely excised.⁵

The Diagnosis: Dermatomyofibroma

Dermatomyofibroma is an uncommon, benign, cutaneous mesenchymal neoplasm composed of fibroblasts and myofibroblasts.^1-3 This skin tumor was first described in 1991 by Hugel⁴ in the German literature as plaquelike fibromatosis. Pediatric dermatomyofibromas are exceedingly rare, with pediatric patients ranging in age from infants to teenagers.¹

Clinically, dermatomyofibromas appear as long-standing, isolated, ill-demarcated, flesh-colored, slightly hyperpigmented or erythematous nodules or plaques that may be raised or indurated.¹ Dermatomyofibromas may present with constant mild pain or pruritus, though in most cases the lesions are asymptomatic.^1,3 The clinical presentation of dermatomyofibroma has a few distinct differences in children compared to adults. In adulthood, dermatomyofibroma has a strong female predominance and most commonly is located on the shoulder and adjacent upper body regions, including the axilla, neck, upper arm, and upper trunk.^1-3 In childhood, the majority of dermatomyofibromas occur in young boys and usually are located on the neck with other upper body regions occurring less frequently.^1,2 A shared characteristic includes the tendency for dermatomyofibromas to have an initial period of enlargement followed by stabilization or slow growth.¹ Reported pediatric lesions have ranged in size from 4 to 60 mm with an average size of 14.9 mm (median, 12 mm).²

The diagnosis of dermatomyofibroma is based on histopathologic features in addition to clinical presentation. Histology from punch biopsy usually reveals a noninvasive dermal proliferation of bland, uniform, slender spindle cells oriented parallel to the overlying epidermis with increased and fragmented elastic fibers.^1,3 Infiltration into the mid or deep dermis is common. The adnexal structures usually are spared; the stroma contains collagen and increased small blood vessels; and there typically is no inflammatory infiltrate, except for occasional scattered mast cells.² Cytologically, the monomorphic spindleshaped tumor cells have an ill-defined, pale, eosinophilic cytoplasm and nuclei that are elongated with tapered edges.³ Dermatomyofibroma has a variable immunohistochemical profile, as it may stain focally positive for CD34 or smooth muscle actin, with occasional staining of factor XIIIa, desmin, calponin, or vimentin.^1-3 Normal to increased levels of often fragmented elastic fibers is a helpful clue in distinguishing dermatomyofibroma from dermatofibroma, hypertrophic scar, dermatofibrosarcoma protuberans, and pilar leiomyoma, in which elastic fibers typically are reduced.³ Differential diagnoses of mesenchymal tumors in children include desmoid fibromatosis, connective tissue nevus, myofibromatosis, and smooth muscle hamartoma.¹

A punch biopsy with clinical observation and followup is recommended for the management of lesions in cosmetically sensitive areas or in very young children who may not tolerate surgery. In symptomatic or cosmetically unappealing cases of dermatomyofibroma, simple surgical excision remains a viable treatment option. Recurrence is uncommon, even if only partially excised, and no instances of metastasis have been reported.^1-5

Dermatomyofibromas may be mistaken for several other entities both benign and malignant. For example, the benign dermatofibroma is the second most common fibrohistiocytic tumor of the skin and presents as a firm, nontender, minimally elevated to dome-shaped papule that usually measures less than or equal to 1 cm in diameter with or without overlying skin changes.^5,6 It primarily is seen in adults with a slight female predominance and favors the lower extremities.⁵ Patients usually are asymptomatic but often report a history of local trauma at the lesion site.⁶ Histologically, dermatofibroma is characterized by a nodular dermal proliferation of spindleshaped fibrous cells and histiocytes in a storiform pattern (Figure 1).⁶ Epidermal induction with acanthosis overlying the tumor often is found with occasional basilar hyperpigmentation.⁵ Dermatofibroma also characteristically has trapped collagen (“collagen balls”) seen at the periphery.^5,6

Piloleiomyomas are benign smooth muscle tumors arising from arrector pili muscles that may be solitary or multiple.⁵ Clinically, they typically present as firm, reddish-brown to flesh-colored papules or nodules that develop more commonly in adulthood.^5,7 Piloleiomyomas favor the extremities and trunk, particularly the shoulder, and can be associated with spontaneous or induced pain. Histologically, piloleiomyomas are well circumscribed and centered within the reticular dermis situated closely to hair follicles (Figure 2).⁵ They are composed of numerous interlacing fascicles or whorls of smooth muscle cells with abundant eosinophilic cytoplasm and blunt-ended, cigar-shaped nuclei.^5,7

Solitary cutaneous myofibroma is a benign fibrous tumor found in adolescents and adults and is the counterpart to infantile myofibromatosis.⁸ Clinically, myofibromas typically present as painless, slow-growing, firm nodules with an occasional bluish hue. Histologically, solitary cutaneous myofibromas appear in a biphasic pattern, with hemangiopericytomatous components as well as spindle cells arranged in short bundles and fascicles resembling leiomyoma (Figure 3). The spindle cells also have abundant eosinophilic cytoplasm with short plump nuclei; the random, irregularly intersecting angles can be used to help differentiate myofibromas from smooth muscle lesions.⁸ Solitary cutaneous myofibroma is in the differential diagnosis for dermatomyofibroma because of their shared myofibroblastic nature.⁹

Dermatofibrosarcoma protuberans (DFSP) is an uncommon, locally invasive sarcoma with a high recurrence rate that favors young to middle-aged adults, with rare childhood onset reported.^5,10,11 Clinically, DFSP typically presents as an asymptomatic, slow-growing, firm, flesh-colored, indurated plaque that develops into a violaceous to reddish-brown nodule.⁵ The atrophic variant of DFSP is characterized by a nonprotuberant lesion and can be especially difficult to distinguish from other entities such as dermatomyofibroma.¹¹ The majority of DFSP lesions occur on the trunk, particularly in the shoulder or pelvic region.⁵ Histologically, early plaque lesions are comprised of monomorphic spindle cells arranged in long fascicles (parallel to the skin surface), infiltrating adnexal structures, and subcutaneous adipocytes in a multilayered honeycomb pattern; the spindle cells of late nodular lesions are arranged in short fascicles in a matted or storiform pattern (Figure 4).^5,10 Early stages of DFSP as well as variations in childhood-onset DFSP can easily be misdiagnosed and incompletely excised.⁵

The Diagnosis: Dermatomyofibroma

Dermatomyofibroma is an uncommon, benign, cutaneous mesenchymal neoplasm composed of fibroblasts and myofibroblasts.^1-3 This skin tumor was first described in 1991 by Hugel⁴ in the German literature as plaquelike fibromatosis. Pediatric dermatomyofibromas are exceedingly rare, with pediatric patients ranging in age from infants to teenagers.¹

Clinically, dermatomyofibromas appear as long-standing, isolated, ill-demarcated, flesh-colored, slightly hyperpigmented or erythematous nodules or plaques that may be raised or indurated.¹ Dermatomyofibromas may present with constant mild pain or pruritus, though in most cases the lesions are asymptomatic.^1,3 The clinical presentation of dermatomyofibroma has a few distinct differences in children compared to adults. In adulthood, dermatomyofibroma has a strong female predominance and most commonly is located on the shoulder and adjacent upper body regions, including the axilla, neck, upper arm, and upper trunk.^1-3 In childhood, the majority of dermatomyofibromas occur in young boys and usually are located on the neck with other upper body regions occurring less frequently.^1,2 A shared characteristic includes the tendency for dermatomyofibromas to have an initial period of enlargement followed by stabilization or slow growth.¹ Reported pediatric lesions have ranged in size from 4 to 60 mm with an average size of 14.9 mm (median, 12 mm).²

The diagnosis of dermatomyofibroma is based on histopathologic features in addition to clinical presentation. Histology from punch biopsy usually reveals a noninvasive dermal proliferation of bland, uniform, slender spindle cells oriented parallel to the overlying epidermis with increased and fragmented elastic fibers.^1,3 Infiltration into the mid or deep dermis is common. The adnexal structures usually are spared; the stroma contains collagen and increased small blood vessels; and there typically is no inflammatory infiltrate, except for occasional scattered mast cells.² Cytologically, the monomorphic spindleshaped tumor cells have an ill-defined, pale, eosinophilic cytoplasm and nuclei that are elongated with tapered edges.³ Dermatomyofibroma has a variable immunohistochemical profile, as it may stain focally positive for CD34 or smooth muscle actin, with occasional staining of factor XIIIa, desmin, calponin, or vimentin.^1-3 Normal to increased levels of often fragmented elastic fibers is a helpful clue in distinguishing dermatomyofibroma from dermatofibroma, hypertrophic scar, dermatofibrosarcoma protuberans, and pilar leiomyoma, in which elastic fibers typically are reduced.³ Differential diagnoses of mesenchymal tumors in children include desmoid fibromatosis, connective tissue nevus, myofibromatosis, and smooth muscle hamartoma.¹

A punch biopsy with clinical observation and followup is recommended for the management of lesions in cosmetically sensitive areas or in very young children who may not tolerate surgery. In symptomatic or cosmetically unappealing cases of dermatomyofibroma, simple surgical excision remains a viable treatment option. Recurrence is uncommon, even if only partially excised, and no instances of metastasis have been reported.^1-5

Dermatomyofibromas may be mistaken for several other entities both benign and malignant. For example, the benign dermatofibroma is the second most common fibrohistiocytic tumor of the skin and presents as a firm, nontender, minimally elevated to dome-shaped papule that usually measures less than or equal to 1 cm in diameter with or without overlying skin changes.^5,6 It primarily is seen in adults with a slight female predominance and favors the lower extremities.⁵ Patients usually are asymptomatic but often report a history of local trauma at the lesion site.⁶ Histologically, dermatofibroma is characterized by a nodular dermal proliferation of spindleshaped fibrous cells and histiocytes in a storiform pattern (Figure 1).⁶ Epidermal induction with acanthosis overlying the tumor often is found with occasional basilar hyperpigmentation.⁵ Dermatofibroma also characteristically has trapped collagen (“collagen balls”) seen at the periphery.^5,6

Piloleiomyomas are benign smooth muscle tumors arising from arrector pili muscles that may be solitary or multiple.⁵ Clinically, they typically present as firm, reddish-brown to flesh-colored papules or nodules that develop more commonly in adulthood.^5,7 Piloleiomyomas favor the extremities and trunk, particularly the shoulder, and can be associated with spontaneous or induced pain. Histologically, piloleiomyomas are well circumscribed and centered within the reticular dermis situated closely to hair follicles (Figure 2).⁵ They are composed of numerous interlacing fascicles or whorls of smooth muscle cells with abundant eosinophilic cytoplasm and blunt-ended, cigar-shaped nuclei.^5,7

Solitary cutaneous myofibroma is a benign fibrous tumor found in adolescents and adults and is the counterpart to infantile myofibromatosis.⁸ Clinically, myofibromas typically present as painless, slow-growing, firm nodules with an occasional bluish hue. Histologically, solitary cutaneous myofibromas appear in a biphasic pattern, with hemangiopericytomatous components as well as spindle cells arranged in short bundles and fascicles resembling leiomyoma (Figure 3). The spindle cells also have abundant eosinophilic cytoplasm with short plump nuclei; the random, irregularly intersecting angles can be used to help differentiate myofibromas from smooth muscle lesions.⁸ Solitary cutaneous myofibroma is in the differential diagnosis for dermatomyofibroma because of their shared myofibroblastic nature.⁹

Dermatofibrosarcoma protuberans (DFSP) is an uncommon, locally invasive sarcoma with a high recurrence rate that favors young to middle-aged adults, with rare childhood onset reported.^5,10,11 Clinically, DFSP typically presents as an asymptomatic, slow-growing, firm, flesh-colored, indurated plaque that develops into a violaceous to reddish-brown nodule.⁵ The atrophic variant of DFSP is characterized by a nonprotuberant lesion and can be especially difficult to distinguish from other entities such as dermatomyofibroma.¹¹ The majority of DFSP lesions occur on the trunk, particularly in the shoulder or pelvic region.⁵ Histologically, early plaque lesions are comprised of monomorphic spindle cells arranged in long fascicles (parallel to the skin surface), infiltrating adnexal structures, and subcutaneous adipocytes in a multilayered honeycomb pattern; the spindle cells of late nodular lesions are arranged in short fascicles in a matted or storiform pattern (Figure 4).^5,10 Early stages of DFSP as well as variations in childhood-onset DFSP can easily be misdiagnosed and incompletely excised.⁵

Practice Gap

Invasive fungal infections are a leading cause of morbidity and mortality among neutropenic, immunocompromised, and critically ill patients. Candida species are the most common cause of fungemia, with portals of entry into the bloodstream including the gastrointestinal tract, contaminated intravascular catheters, and localized foci of infection.¹ Diagnosis of invasive candidiasis remains challenging due to an absence of specific clinical signs and symptoms, varying from a mild fever that is unresponsive to antibiotics to florid sepsis. When present, clinical clues may include chorioretinitis; muscle abscesses; and skin eruptions, characteristically with Candida tropicalis. Cutaneous manifestations of disseminated Candida infections appear in only 13% of affected patients.¹ The lesions typically present as 5- to 10-mm pink dermal papules or painless pustules on an erythematous base and may be singular, localized, or diffuse in distribution. Body regions normally involved are the trunk, arms, and legs, rarely the head and neck.¹ Cutaneous lesions often develop at a time when patients are febrile, are not responding to antibiotics, and are clinically deteriorating.

A 15-year-old adolescent boy with pre–B-cell acute lymphoblastic leukemia was admitted with febrile neutropenia for presumed septic shock secondary to an unknown infectious etiology. The patient was started on broad-spectrum intravenous antibiotics, and blood cultures were obtained. On the second day of hospitalization, he developed approximately 10 to 15 discrete, 3- to 6-mm, pink to violaceous papules scattered on the chest and arms (Figure 1). Over several hours, the number of lesions increased to more than 50 with involvement of the legs (Figure 2). A punch biopsy of lesional skin from the left dorsal wrist demonstrated a circumscribed abscess of yeast in the papillary dermis, which was highlighted by periodic acid–Schiff staining with minimal associated inflammation (Figure 3). Blood and tissue cultures persistently grew C tropicalis. The patient was started on intravenous liposomal amphotericin B but died on day 5 of hospitalization after developing endocarditis.

Early and reliable diagnosis of Candida species fungemia is of critical importance to successful treatment, particularly with the emergence of multidrug-resistant strains such as Candida auris.² In patients with apparent cutaneous manifestations, a lesional punch biopsy for culture and histopathologic evaluation is recommended in addition to blood culture; however, organisms may or may not be present in large numbers, and they may be difficult to identify on routine hematoxylin and eosin–stained tissue sections. To enhance the likelihood of highlighting the fungus within the sample, the pathologist must be made aware of the presumptive diagnosis of disseminated candidiasis so that special techniques can be utilized, such as periodic acid–Schiff stain.

Although positive blood culture is the gold standard for candidemia diagnosis, only 30% to 50% of patients with disseminated candidiasis had positive blood cultures at autopsy.¹ Another study showed the sensitivity of blood culture for the detection of invasive fungal infection to be as low as 8.3%.³ In cases with positive blood cultures, the median time to positivity is 2 to 3 days, but it can take as long as 8 days, thus limiting its clinical utility in acutely ill patients.⁴ Given the low sensitivity and prolonged time required for culture growth of most fungal organisms, novel assays for rapid, non–culture-based diagnosis of systemic fungal infections hold substantial clinical promise moving forward.

The Technique

One of the more promising non–culture-based fungal diagnostic methodologies is an antigen assay based on the detection of serum (1,3)-β-D-glucan (BDG), a major cell wall constituent of most pathogenic fungi. This assay is not specific for Candida species and can be positive for Aspergillosis species, Fusarium species, Coccidioides immitis, Histoplasma capsulatum, and Pneumocystis jirovecii pneumonia, among others; therefore, it functions as a general biomarker for fungi in the bloodstream.^4,5 (1,3)-β-D-glucan assay can be useful as an adjunct for blood cultures and punch biopsy, especially when cultures are negative or the results remain outstanding. The results of the BDG assay are available in less than 24 hours at minimal cost, and the test is approved by the US Food and Drug Administration for use as an aid in invasive fungal disease diagnosis. In a meta-analysis of 11 studies, BDG sensitivity was 75%.⁴ In a study based on autopsy cases from 6 years, BDG specificity was 98.4% with positive and negative predictive values of 86.7% and 97.1%, respectively.³ Optimal results were achieved when 2 consecutive tests were positive.⁴ The serum assay output is based on spectrophotometer readings, which are converted to BDG concentrations (negative, <60 pg/mL; indeterminate, 60–79 pg/mL; positive ≥80 pg/mL).⁵ Although we cannot be certain, utilizing the BDG assay in our patient may have led to earlier treatment and a better outcome.

A disadvantage of the BDG assay is the potential for false-positive results, which have been reported in lung transplant recipients with respiratory mold colonization and patients with other systemic bacterial infections.⁴ False-positive results also have been associated with use of ampicillin-clavulanate and piperacillin-tazobactam antibiotics and human blood products, hemodialysis, and severe mucositis, thus reaffirming the importance of judicious interpretation of BDG assay results by the clinician.^4,6 There also is a potential for false-negative results, as the BDG assay does not detect certain fungal species such as Cryptococcus species and Blastomyces dermatitidis, which produce very low levels of BDG, or zygomycetes (Absidia, Mucor, and Rizopus species), which are not known to produce BDG.⁶

Practice Implications

In the setting of invasive fungal infections, a high degree of clinical suspicion is paramount due to the often subtle nature of cutaneous manifestations. A positive BDG assay can be used to identify high-risk patients for empiric antifungal therapy, prompting early intervention and improved outcomes in these acutely ill patients. The BDG assay’s excellent negative predictive value is useful in ruling out invasive Candida infections and may justify stopping unnecessary empiric antifungal therapy.⁴ For the dermatology hospitalist, incorporation of the BDG assay as a noninvasive screening tool may allow for more rapid initiation of appropriate antifungal therapy while awaiting confirmatory skin biopsy or culture results in disseminated candidemia and other invasive fungal infections.

Practice Gap

Invasive fungal infections are a leading cause of morbidity and mortality among neutropenic, immunocompromised, and critically ill patients. Candida species are the most common cause of fungemia, with portals of entry into the bloodstream including the gastrointestinal tract, contaminated intravascular catheters, and localized foci of infection.¹ Diagnosis of invasive candidiasis remains challenging due to an absence of specific clinical signs and symptoms, varying from a mild fever that is unresponsive to antibiotics to florid sepsis. When present, clinical clues may include chorioretinitis; muscle abscesses; and skin eruptions, characteristically with Candida tropicalis. Cutaneous manifestations of disseminated Candida infections appear in only 13% of affected patients.¹ The lesions typically present as 5- to 10-mm pink dermal papules or painless pustules on an erythematous base and may be singular, localized, or diffuse in distribution. Body regions normally involved are the trunk, arms, and legs, rarely the head and neck.¹ Cutaneous lesions often develop at a time when patients are febrile, are not responding to antibiotics, and are clinically deteriorating.

A 15-year-old adolescent boy with pre–B-cell acute lymphoblastic leukemia was admitted with febrile neutropenia for presumed septic shock secondary to an unknown infectious etiology. The patient was started on broad-spectrum intravenous antibiotics, and blood cultures were obtained. On the second day of hospitalization, he developed approximately 10 to 15 discrete, 3- to 6-mm, pink to violaceous papules scattered on the chest and arms (Figure 1). Over several hours, the number of lesions increased to more than 50 with involvement of the legs (Figure 2). A punch biopsy of lesional skin from the left dorsal wrist demonstrated a circumscribed abscess of yeast in the papillary dermis, which was highlighted by periodic acid–Schiff staining with minimal associated inflammation (Figure 3). Blood and tissue cultures persistently grew C tropicalis. The patient was started on intravenous liposomal amphotericin B but died on day 5 of hospitalization after developing endocarditis.

Early and reliable diagnosis of Candida species fungemia is of critical importance to successful treatment, particularly with the emergence of multidrug-resistant strains such as Candida auris.² In patients with apparent cutaneous manifestations, a lesional punch biopsy for culture and histopathologic evaluation is recommended in addition to blood culture; however, organisms may or may not be present in large numbers, and they may be difficult to identify on routine hematoxylin and eosin–stained tissue sections. To enhance the likelihood of highlighting the fungus within the sample, the pathologist must be made aware of the presumptive diagnosis of disseminated candidiasis so that special techniques can be utilized, such as periodic acid–Schiff stain.

Although positive blood culture is the gold standard for candidemia diagnosis, only 30% to 50% of patients with disseminated candidiasis had positive blood cultures at autopsy.¹ Another study showed the sensitivity of blood culture for the detection of invasive fungal infection to be as low as 8.3%.³ In cases with positive blood cultures, the median time to positivity is 2 to 3 days, but it can take as long as 8 days, thus limiting its clinical utility in acutely ill patients.⁴ Given the low sensitivity and prolonged time required for culture growth of most fungal organisms, novel assays for rapid, non–culture-based diagnosis of systemic fungal infections hold substantial clinical promise moving forward.

The Technique

One of the more promising non–culture-based fungal diagnostic methodologies is an antigen assay based on the detection of serum (1,3)-β-D-glucan (BDG), a major cell wall constituent of most pathogenic fungi. This assay is not specific for Candida species and can be positive for Aspergillosis species, Fusarium species, Coccidioides immitis, Histoplasma capsulatum, and Pneumocystis jirovecii pneumonia, among others; therefore, it functions as a general biomarker for fungi in the bloodstream.^4,5 (1,3)-β-D-glucan assay can be useful as an adjunct for blood cultures and punch biopsy, especially when cultures are negative or the results remain outstanding. The results of the BDG assay are available in less than 24 hours at minimal cost, and the test is approved by the US Food and Drug Administration for use as an aid in invasive fungal disease diagnosis. In a meta-analysis of 11 studies, BDG sensitivity was 75%.⁴ In a study based on autopsy cases from 6 years, BDG specificity was 98.4% with positive and negative predictive values of 86.7% and 97.1%, respectively.³ Optimal results were achieved when 2 consecutive tests were positive.⁴ The serum assay output is based on spectrophotometer readings, which are converted to BDG concentrations (negative, <60 pg/mL; indeterminate, 60–79 pg/mL; positive ≥80 pg/mL).⁵ Although we cannot be certain, utilizing the BDG assay in our patient may have led to earlier treatment and a better outcome.

A disadvantage of the BDG assay is the potential for false-positive results, which have been reported in lung transplant recipients with respiratory mold colonization and patients with other systemic bacterial infections.⁴ False-positive results also have been associated with use of ampicillin-clavulanate and piperacillin-tazobactam antibiotics and human blood products, hemodialysis, and severe mucositis, thus reaffirming the importance of judicious interpretation of BDG assay results by the clinician.^4,6 There also is a potential for false-negative results, as the BDG assay does not detect certain fungal species such as Cryptococcus species and Blastomyces dermatitidis, which produce very low levels of BDG, or zygomycetes (Absidia, Mucor, and Rizopus species), which are not known to produce BDG.⁶

Practice Implications

In the setting of invasive fungal infections, a high degree of clinical suspicion is paramount due to the often subtle nature of cutaneous manifestations. A positive BDG assay can be used to identify high-risk patients for empiric antifungal therapy, prompting early intervention and improved outcomes in these acutely ill patients. The BDG assay’s excellent negative predictive value is useful in ruling out invasive Candida infections and may justify stopping unnecessary empiric antifungal therapy.⁴ For the dermatology hospitalist, incorporation of the BDG assay as a noninvasive screening tool may allow for more rapid initiation of appropriate antifungal therapy while awaiting confirmatory skin biopsy or culture results in disseminated candidemia and other invasive fungal infections.

Practice Gap

Invasive fungal infections are a leading cause of morbidity and mortality among neutropenic, immunocompromised, and critically ill patients. Candida species are the most common cause of fungemia, with portals of entry into the bloodstream including the gastrointestinal tract, contaminated intravascular catheters, and localized foci of infection.¹ Diagnosis of invasive candidiasis remains challenging due to an absence of specific clinical signs and symptoms, varying from a mild fever that is unresponsive to antibiotics to florid sepsis. When present, clinical clues may include chorioretinitis; muscle abscesses; and skin eruptions, characteristically with Candida tropicalis. Cutaneous manifestations of disseminated Candida infections appear in only 13% of affected patients.¹ The lesions typically present as 5- to 10-mm pink dermal papules or painless pustules on an erythematous base and may be singular, localized, or diffuse in distribution. Body regions normally involved are the trunk, arms, and legs, rarely the head and neck.¹ Cutaneous lesions often develop at a time when patients are febrile, are not responding to antibiotics, and are clinically deteriorating.

A 15-year-old adolescent boy with pre–B-cell acute lymphoblastic leukemia was admitted with febrile neutropenia for presumed septic shock secondary to an unknown infectious etiology. The patient was started on broad-spectrum intravenous antibiotics, and blood cultures were obtained. On the second day of hospitalization, he developed approximately 10 to 15 discrete, 3- to 6-mm, pink to violaceous papules scattered on the chest and arms (Figure 1). Over several hours, the number of lesions increased to more than 50 with involvement of the legs (Figure 2). A punch biopsy of lesional skin from the left dorsal wrist demonstrated a circumscribed abscess of yeast in the papillary dermis, which was highlighted by periodic acid–Schiff staining with minimal associated inflammation (Figure 3). Blood and tissue cultures persistently grew C tropicalis. The patient was started on intravenous liposomal amphotericin B but died on day 5 of hospitalization after developing endocarditis.

Early and reliable diagnosis of Candida species fungemia is of critical importance to successful treatment, particularly with the emergence of multidrug-resistant strains such as Candida auris.² In patients with apparent cutaneous manifestations, a lesional punch biopsy for culture and histopathologic evaluation is recommended in addition to blood culture; however, organisms may or may not be present in large numbers, and they may be difficult to identify on routine hematoxylin and eosin–stained tissue sections. To enhance the likelihood of highlighting the fungus within the sample, the pathologist must be made aware of the presumptive diagnosis of disseminated candidiasis so that special techniques can be utilized, such as periodic acid–Schiff stain.

Although positive blood culture is the gold standard for candidemia diagnosis, only 30% to 50% of patients with disseminated candidiasis had positive blood cultures at autopsy.¹ Another study showed the sensitivity of blood culture for the detection of invasive fungal infection to be as low as 8.3%.³ In cases with positive blood cultures, the median time to positivity is 2 to 3 days, but it can take as long as 8 days, thus limiting its clinical utility in acutely ill patients.⁴ Given the low sensitivity and prolonged time required for culture growth of most fungal organisms, novel assays for rapid, non–culture-based diagnosis of systemic fungal infections hold substantial clinical promise moving forward.

The Technique

One of the more promising non–culture-based fungal diagnostic methodologies is an antigen assay based on the detection of serum (1,3)-β-D-glucan (BDG), a major cell wall constituent of most pathogenic fungi. This assay is not specific for Candida species and can be positive for Aspergillosis species, Fusarium species, Coccidioides immitis, Histoplasma capsulatum, and Pneumocystis jirovecii pneumonia, among others; therefore, it functions as a general biomarker for fungi in the bloodstream.^4,5 (1,3)-β-D-glucan assay can be useful as an adjunct for blood cultures and punch biopsy, especially when cultures are negative or the results remain outstanding. The results of the BDG assay are available in less than 24 hours at minimal cost, and the test is approved by the US Food and Drug Administration for use as an aid in invasive fungal disease diagnosis. In a meta-analysis of 11 studies, BDG sensitivity was 75%.⁴ In a study based on autopsy cases from 6 years, BDG specificity was 98.4% with positive and negative predictive values of 86.7% and 97.1%, respectively.³ Optimal results were achieved when 2 consecutive tests were positive.⁴ The serum assay output is based on spectrophotometer readings, which are converted to BDG concentrations (negative, <60 pg/mL; indeterminate, 60–79 pg/mL; positive ≥80 pg/mL).⁵ Although we cannot be certain, utilizing the BDG assay in our patient may have led to earlier treatment and a better outcome.

A disadvantage of the BDG assay is the potential for false-positive results, which have been reported in lung transplant recipients with respiratory mold colonization and patients with other systemic bacterial infections.⁴ False-positive results also have been associated with use of ampicillin-clavulanate and piperacillin-tazobactam antibiotics and human blood products, hemodialysis, and severe mucositis, thus reaffirming the importance of judicious interpretation of BDG assay results by the clinician.^4,6 There also is a potential for false-negative results, as the BDG assay does not detect certain fungal species such as Cryptococcus species and Blastomyces dermatitidis, which produce very low levels of BDG, or zygomycetes (Absidia, Mucor, and Rizopus species), which are not known to produce BDG.⁶

Practice Implications

In the setting of invasive fungal infections, a high degree of clinical suspicion is paramount due to the often subtle nature of cutaneous manifestations. A positive BDG assay can be used to identify high-risk patients for empiric antifungal therapy, prompting early intervention and improved outcomes in these acutely ill patients. The BDG assay’s excellent negative predictive value is useful in ruling out invasive Candida infections and may justify stopping unnecessary empiric antifungal therapy.⁴ For the dermatology hospitalist, incorporation of the BDG assay as a noninvasive screening tool may allow for more rapid initiation of appropriate antifungal therapy while awaiting confirmatory skin biopsy or culture results in disseminated candidemia and other invasive fungal infections.