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Answer
Digital mucous cysts (choice “c”), also known as myxoid cysts, are quite common and are found often on fingers and occasionally on toes. But they are almost always located on the distal dorsal portion of the digit, between the cuticle and distal interphalangeal joint—close enough, in many cases, to compress the nail matrix, which leads to a longitudinal trough in the nail plate. Surface erosion of these lesions is unusual but is occasionally seen.
However, given the history, appearance, and especially the location of this patient’s lesion, this is the one diagnosis our patient almost certainly did not have. The others, discussed below, were all real possibilities, and since “common things occur commonly,” squamous cell carcinoma was the most likely.
Discussion
With this clinical picture, cancer is assumed until proven otherwise. In that regard, the presence of a longstanding wart in this location is especially significant, since human papillomavirus (HPV) is known to be potentially oncogenic. The patient’s heavily sun-damaged skin adds another layer of risk for malignant transformation.
The only way to sort through this differential diagnosis was to perform a shave biopsy, which confirmed the diagnosis of squamous cell carcinoma (SCC)—one that showed evidence of arising from a long-standing wart. The patient was referred for Mohs micrographic surgery, for two reasons: (1) this location does not lend itself to simple excision and closure, both because of the paucity of adjacent skin and because of the potential for damage to the underlying tendons, nerves, and blood supply, and (2) SCCs of nonsolar causation (besides HPV, these include ionizing radiation, arsenic, and chronic ulcers) have more potential for metastasis than do the far more common sun-caused SCCs. This is all the more reason to obtain adequate margins. Often in such cases, irradiation of the site is also done, postoperatively.
Had the biopsy not shown clear evidence of cancer, the other items in the differential diagnosis would have come into play. This would have necessitated an additional biopsy, this time to obtain tissue for acid-fast bacilli and bacterial and fungal cultures.
As of this writing, the patient is awaiting Mohs surgery. He will have to be followed closely for at least a year to watch for any signs of metastasis. With an intact immune system, his prognosis is excellent.
Answer
Digital mucous cysts (choice “c”), also known as myxoid cysts, are quite common and are found often on fingers and occasionally on toes. But they are almost always located on the distal dorsal portion of the digit, between the cuticle and distal interphalangeal joint—close enough, in many cases, to compress the nail matrix, which leads to a longitudinal trough in the nail plate. Surface erosion of these lesions is unusual but is occasionally seen.
However, given the history, appearance, and especially the location of this patient’s lesion, this is the one diagnosis our patient almost certainly did not have. The others, discussed below, were all real possibilities, and since “common things occur commonly,” squamous cell carcinoma was the most likely.
Discussion
With this clinical picture, cancer is assumed until proven otherwise. In that regard, the presence of a longstanding wart in this location is especially significant, since human papillomavirus (HPV) is known to be potentially oncogenic. The patient’s heavily sun-damaged skin adds another layer of risk for malignant transformation.
The only way to sort through this differential diagnosis was to perform a shave biopsy, which confirmed the diagnosis of squamous cell carcinoma (SCC)—one that showed evidence of arising from a long-standing wart. The patient was referred for Mohs micrographic surgery, for two reasons: (1) this location does not lend itself to simple excision and closure, both because of the paucity of adjacent skin and because of the potential for damage to the underlying tendons, nerves, and blood supply, and (2) SCCs of nonsolar causation (besides HPV, these include ionizing radiation, arsenic, and chronic ulcers) have more potential for metastasis than do the far more common sun-caused SCCs. This is all the more reason to obtain adequate margins. Often in such cases, irradiation of the site is also done, postoperatively.
Had the biopsy not shown clear evidence of cancer, the other items in the differential diagnosis would have come into play. This would have necessitated an additional biopsy, this time to obtain tissue for acid-fast bacilli and bacterial and fungal cultures.
As of this writing, the patient is awaiting Mohs surgery. He will have to be followed closely for at least a year to watch for any signs of metastasis. With an intact immune system, his prognosis is excellent.
Answer
Digital mucous cysts (choice “c”), also known as myxoid cysts, are quite common and are found often on fingers and occasionally on toes. But they are almost always located on the distal dorsal portion of the digit, between the cuticle and distal interphalangeal joint—close enough, in many cases, to compress the nail matrix, which leads to a longitudinal trough in the nail plate. Surface erosion of these lesions is unusual but is occasionally seen.
However, given the history, appearance, and especially the location of this patient’s lesion, this is the one diagnosis our patient almost certainly did not have. The others, discussed below, were all real possibilities, and since “common things occur commonly,” squamous cell carcinoma was the most likely.
Discussion
With this clinical picture, cancer is assumed until proven otherwise. In that regard, the presence of a longstanding wart in this location is especially significant, since human papillomavirus (HPV) is known to be potentially oncogenic. The patient’s heavily sun-damaged skin adds another layer of risk for malignant transformation.
The only way to sort through this differential diagnosis was to perform a shave biopsy, which confirmed the diagnosis of squamous cell carcinoma (SCC)—one that showed evidence of arising from a long-standing wart. The patient was referred for Mohs micrographic surgery, for two reasons: (1) this location does not lend itself to simple excision and closure, both because of the paucity of adjacent skin and because of the potential for damage to the underlying tendons, nerves, and blood supply, and (2) SCCs of nonsolar causation (besides HPV, these include ionizing radiation, arsenic, and chronic ulcers) have more potential for metastasis than do the far more common sun-caused SCCs. This is all the more reason to obtain adequate margins. Often in such cases, irradiation of the site is also done, postoperatively.
Had the biopsy not shown clear evidence of cancer, the other items in the differential diagnosis would have come into play. This would have necessitated an additional biopsy, this time to obtain tissue for acid-fast bacilli and bacterial and fungal cultures.
As of this writing, the patient is awaiting Mohs surgery. He will have to be followed closely for at least a year to watch for any signs of metastasis. With an intact immune system, his prognosis is excellent.
An 87-year-old man presents for evaluation of a lesion on his left fifth finger that has grown and become ulcerated in the past five months. There is almost no pain in the lesion, which the patient insists was a “wart” for the 40 years prior to these recent changes. Over the years, he has treated his wart with acids, curettement, and liquid nitrogen, to no effect. A recent seven-day course of cephalexin (500 mg tid) also failed to help. Additional history taking reveals that the patient is a farmer who spent his entire life working outdoors every day, year-round. There is no history of immunosuppression. His medications include metoprolol and hydrochlorothiazide. Closer inspection of the lesion reveals a 9-mm, centrally eroded nodule overlying the dorsal proximal interphalangeal joint. The lesion is quite firm on palpation, with a surface that looks and feels smooth and is nontender, with minimal redness. There are no palpable nodes in the epitrochlear or axillary locations. Elsewhere, the patient’s skin is remarkably sun-damaged, with numerous actinic keratoses, solar lentigines, and solar atrophy evident, especially on his hands.
