Bluish Pink, Nontender Lesion Worries Patient’s Mother

A 12-year-old girl is brought to dermatology by her mother for evaluation of a lesion on her arm. It’s been there for two years without causing symptoms—but lately it has grown, as has the mother’s concern.

The child is otherwise healthy. The mother reports that the child has neither a personal nor a family history of seizures.

EXAMINATION
A solitary, firm, subcutaneous nodule measuring 2 cm is located on the lateral aspect of the child’s left triceps. It is bluish pink, nontender, and firm on palpation. No other overlying skin changes are seen.

Lateral digital traction toward the center of the lesion produces no dimpling, while lateral traction toward its periphery accentuates the lesion’s central raised portion. The lesion is moderately mobile. No lymph nodes are felt on palpation of nodal sites in the area, and no other such lesions are found elsewhere on the child’s skin.

What is the diagnosis?

DISCUSSION
At this point, the differential included items such as pilomatricoma, dermatofibroma, calcinosis cutis, or epidermal cyst. The firm feel, bluish color, and shallow subcutaneous location of the lesion lent themselves to a provisional diagnosis of pilomatricoma, as did the patient’s age. But the fact that the lesion was changing was of sufficient concern to prompt removal.

Excision revealed a cystic lesion with cottage-cheese­­–like contents and a poorly defined wall, extending more than a centimeter into the subcutaneous tissue. It was removed in one piece and submitted to pathology. Primary closure completed the procedure.

The pathology report showed sheets of anucleate squamous cells (called ghost cells), benign viable nucleated squamous cells, and a center filled with multiple soft calcified granules. A positive von Kossa stain confirmed the expected diagnosis of pilomatricoma (PMC; also spelled pilomatrixoma).

PMCs, also known by their eponymous designation of calcifying epithelioma of Malherbe, are common, benign appendageal tumors derived from hair matrix. They usually manifest (as in this case) as a solitary subcutaneous firm mass, often with bluish discoloration, on the face, neck, or upper extremities. While they average around 2 cm, they can be as large as 15 cm in diameter. They are more common in children and occur slightly more often in girls.

There is some evidence that the tendency to develop PMCs is associated with increased levels of beta-catenin, which encourages cell growth by diminishing apoptosis. This mechanism is thought to promote malignant transformation of PMCs—a  rare event.

As is often the case, the main concern about this patient’s lesion related to its unknown source and recent alteration. Aside from scarring, the patient was no worse off for its removal—and her mother was much relieved.

TAKE-HOME LEARNING POINTS
• PMCs are benign cystic lesions of appendageal origin, commonly found on the necks, faces, and upper extremities of children.

• Diagnostic clues for PMC include firm feel, subcutaneous location, bluish discoloration, and patient age.

• PMCs have poorly defined cyst walls and granular calcified contents.

• Except when occurring in multiples, PMCs have no pathologic implications.

• The term calcifying epithelioma of Malherbe is still in use, as is the alternate spelling of pilomatrixoma. 

A 12-year-old girl is brought to dermatology by her mother for evaluation of a lesion on her arm. It’s been there for two years without causing symptoms—but lately it has grown, as has the mother’s concern.

The child is otherwise healthy. The mother reports that the child has neither a personal nor a family history of seizures.

EXAMINATION
A solitary, firm, subcutaneous nodule measuring 2 cm is located on the lateral aspect of the child’s left triceps. It is bluish pink, nontender, and firm on palpation. No other overlying skin changes are seen.

Lateral digital traction toward the center of the lesion produces no dimpling, while lateral traction toward its periphery accentuates the lesion’s central raised portion. The lesion is moderately mobile. No lymph nodes are felt on palpation of nodal sites in the area, and no other such lesions are found elsewhere on the child’s skin.

What is the diagnosis?

DISCUSSION
At this point, the differential included items such as pilomatricoma, dermatofibroma, calcinosis cutis, or epidermal cyst. The firm feel, bluish color, and shallow subcutaneous location of the lesion lent themselves to a provisional diagnosis of pilomatricoma, as did the patient’s age. But the fact that the lesion was changing was of sufficient concern to prompt removal.

Excision revealed a cystic lesion with cottage-cheese­­–like contents and a poorly defined wall, extending more than a centimeter into the subcutaneous tissue. It was removed in one piece and submitted to pathology. Primary closure completed the procedure.

The pathology report showed sheets of anucleate squamous cells (called ghost cells), benign viable nucleated squamous cells, and a center filled with multiple soft calcified granules. A positive von Kossa stain confirmed the expected diagnosis of pilomatricoma (PMC; also spelled pilomatrixoma).

PMCs, also known by their eponymous designation of calcifying epithelioma of Malherbe, are common, benign appendageal tumors derived from hair matrix. They usually manifest (as in this case) as a solitary subcutaneous firm mass, often with bluish discoloration, on the face, neck, or upper extremities. While they average around 2 cm, they can be as large as 15 cm in diameter. They are more common in children and occur slightly more often in girls.

There is some evidence that the tendency to develop PMCs is associated with increased levels of beta-catenin, which encourages cell growth by diminishing apoptosis. This mechanism is thought to promote malignant transformation of PMCs—a  rare event.

As is often the case, the main concern about this patient’s lesion related to its unknown source and recent alteration. Aside from scarring, the patient was no worse off for its removal—and her mother was much relieved.

TAKE-HOME LEARNING POINTS
• PMCs are benign cystic lesions of appendageal origin, commonly found on the necks, faces, and upper extremities of children.

• Diagnostic clues for PMC include firm feel, subcutaneous location, bluish discoloration, and patient age.

• PMCs have poorly defined cyst walls and granular calcified contents.

• Except when occurring in multiples, PMCs have no pathologic implications.

• The term calcifying epithelioma of Malherbe is still in use, as is the alternate spelling of pilomatrixoma. 

A 12-year-old girl is brought to dermatology by her mother for evaluation of a lesion on her arm. It’s been there for two years without causing symptoms—but lately it has grown, as has the mother’s concern.

The child is otherwise healthy. The mother reports that the child has neither a personal nor a family history of seizures.

EXAMINATION
A solitary, firm, subcutaneous nodule measuring 2 cm is located on the lateral aspect of the child’s left triceps. It is bluish pink, nontender, and firm on palpation. No other overlying skin changes are seen.

Lateral digital traction toward the center of the lesion produces no dimpling, while lateral traction toward its periphery accentuates the lesion’s central raised portion. The lesion is moderately mobile. No lymph nodes are felt on palpation of nodal sites in the area, and no other such lesions are found elsewhere on the child’s skin.

What is the diagnosis?

DISCUSSION
At this point, the differential included items such as pilomatricoma, dermatofibroma, calcinosis cutis, or epidermal cyst. The firm feel, bluish color, and shallow subcutaneous location of the lesion lent themselves to a provisional diagnosis of pilomatricoma, as did the patient’s age. But the fact that the lesion was changing was of sufficient concern to prompt removal.

Excision revealed a cystic lesion with cottage-cheese­­–like contents and a poorly defined wall, extending more than a centimeter into the subcutaneous tissue. It was removed in one piece and submitted to pathology. Primary closure completed the procedure.

The pathology report showed sheets of anucleate squamous cells (called ghost cells), benign viable nucleated squamous cells, and a center filled with multiple soft calcified granules. A positive von Kossa stain confirmed the expected diagnosis of pilomatricoma (PMC; also spelled pilomatrixoma).

PMCs, also known by their eponymous designation of calcifying epithelioma of Malherbe, are common, benign appendageal tumors derived from hair matrix. They usually manifest (as in this case) as a solitary subcutaneous firm mass, often with bluish discoloration, on the face, neck, or upper extremities. While they average around 2 cm, they can be as large as 15 cm in diameter. They are more common in children and occur slightly more often in girls.

There is some evidence that the tendency to develop PMCs is associated with increased levels of beta-catenin, which encourages cell growth by diminishing apoptosis. This mechanism is thought to promote malignant transformation of PMCs—a  rare event.

As is often the case, the main concern about this patient’s lesion related to its unknown source and recent alteration. Aside from scarring, the patient was no worse off for its removal—and her mother was much relieved.

TAKE-HOME LEARNING POINTS
• PMCs are benign cystic lesions of appendageal origin, commonly found on the necks, faces, and upper extremities of children.

• Diagnostic clues for PMC include firm feel, subcutaneous location, bluish discoloration, and patient age.

• PMCs have poorly defined cyst walls and granular calcified contents.

• Except when occurring in multiples, PMCs have no pathologic implications.

• The term calcifying epithelioma of Malherbe is still in use, as is the alternate spelling of pilomatrixoma.