Giant cell collagenoma in a patient with Cowden syndrome: A rare case report and literature review with a focus on the spectrum of sclerotic fibroma and giant cell collagenoma.

Sclerotic fibroma (SF) is a rare subset of dermal fibromas that occurs sporadically or in association with Cowden syndrome (CS). We report a case of a patient with known CS and a solitary lesion on the scalp. Histologic examination demonstrated a well-circumscribed lesion with sclerotic dermis and a whorled collagen pattern, multinucleated giant cells, and dendritic spindle cells. Nuclear atypia or mitotic figures were not noted. The giant cells were negative for Melan-A, SOX-10, EMA, SOX-10, and factor XIIIa. These findings are consistent with a giant cell collagenoma (GCC). Despite possible overlap with SF, GCC has not been associated with CS. This makes our case unique and suggests that GCC should be included in the spectrum of CS-associated cutaneous lesions. The diagnosis of SF may lead to the identification of previously undiagnosed CS; accordingly, GCC, even when present as a solitary lesion, may indicate the need for further work-up and screening for CS.