Storiform collagenoma: case report.

Storiform collagenoma is a rare tumor, which originates from the proliferation of fibroblasts that show increased production of type-I collagen. It is usually found in the face, neck and extremities, but it can also appear in the trunk, scalp and, less frequently, in the oral mucosa and the nail bed. It affects both sexes, with a slight female predominance. It may be solitary or multiple, the latter being an important marker for Cowden syndrome. It presents as a painless, solid nodular tumor that is slow-growing. It must be considered in the differential diagnosis of other well-circumscribed skin lesions, such as dermatofibroma, pleomorphic fibroma, sclerotic lipoma, fibrolipoma, giant cell collagenoma, benign fibrous histiocytoma, intradermal Spitz nevus and giant cell angiohistiocytoma.