Abstract

Phosphatase and tensin homolog (PTEN) is a tumor suppressor gene that encodes PTEN phosphatase. Inactivation of the PTEN gene by germline mutations results in PTEN-hamartoma tumor syndrome (PHTS) and Cowden syndrome (CS). Clinically, CS leads to hamartomatous tumors in different organs. Skin lesions associated with PHTS include multiple trichilemmomas, oral papillomas, mucocutaneous fibromas and neuromas and acral and/or palmoplantar keratoses. Sclerotic fibroma is a distinct fibroma seen in CS, characterized by bland CD34-positive dendritic spindle cells embedded in a sclerotic stroma with a wood-grain pattern of clefting. A 48-year-old male presented with a cyst on his scalp. He had a history of thyroid nodule, pheochromocytoma and PHTS, with a documented mutation in the PTEN gene. Prior dermatologic history included sclerotic fibroma, collagenoma, and trichilemmoma. The lesion was a 1.5 cm firm mobile nodule on the right scalp. An excisional specimen revealed a tumor occupying the dermis and extending into the subcutis, characterized by slender, stellate, and plump dendritic cells embedded in a sclerotic stroma, with clefts imparting a wood-grain pattern. There were scattered multinucleate floret cells. CD34 stained the dendritic processes. The multinucleated cells showed variable staining. These were negative for Factor 13a. immunohistochemical staining for PTEN was negative in the tumor. The floret cell component and subcutaneous extension are unique features, not previously reported in sclerotic fibromas. Alternatively, this tumor may represent a giant cell collagenoma, which is histopathologically similar to sclerotic fibroma but has not been reported in CS. Documenting negative expression of PTEN by immunohistochemistry is also a unique and potentially helpful use of the antibody in potential CS neoplasms.

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