Benign Histiocytoma With Features Of A So-Called Storiform Collagenoma

Storiform collagenoma/sclerotic fibroma usually presents as a solitary, solid, nodular and painless mass in the head and neck region, extremities, trunk and not infrequently in the nail bed. Multiple lesions occur in the setting of Cowden syndrome. The tumor has also been reported to arise in patients with Rubinstein-Taybi syndrome. The tumor is paucicellular and composed of bland appearing spindle cells surrounded by a dense collagen matrix.

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Slide 1: 55 year-old man with a leg nodule. There is a very extensive pattern of dermal fibroplasia. There is an epidermal collarette that demarcates this lesion from the epidermis.

Slide 2: The lesion assumes a distinct storiform pattern with rather excessive collagenosis.

Slide 3: The defining cells exhibit stellate scalloped nuclear contours. The findings are highly characteristic for a storiform collagenoma.