Abstract:

A 21-year-old male presented with a single tender, skin-colored, pedunculated 0.5 cm papulonodule on his left scalp gradually increasing in size over two years. The lesion was repeatedly traumatized by haircuts and required work headgear. Shave biopsy revealed a well circumscribed but unencapsulated dome shaped proliferation of hyalinized clefted collagen with an overlying atrophic epidermis. Fusiform and stellate cells intercalate through collagen. Multinucleated giant cells are prominent with hyperchromatic and enlarged nuclei, but no mitotic figures. Staining with CD34 outlined the collagen clefts and stained the majority of the fusiform and giant cells. Factor XIIIa also stained a portion of these cells. Acid muchopolysaccharide stain highlighted mucin within the collagen clefts. S100 stained scattered dendritic cells. These findings combine features of pleomorphic fibroma and sclerotic fibroma, which led to the descriptive name of pleomorphic sclerotic fibroma. While rare, this case highlights an important benign variant easily mistaken for malignancy given the atypical features of the fusiform and giant cells. The slow growth pattern, rare recurrence, and lack of mitotic figures are reassuring signs. The atypical cytologic changes are considered degenerative, and are found in other benign pleomorphic neoplasms. Awareness of this benign entity is necessary to avoid potentially invasive follow up procedures.

Financial Disclosure:
No current or relevant financial relationships exist.

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Andy Gould, DO