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April 2011

A Firm Nodule on the Arm—Diagnosis

Author Affiliations
 

MARY S.STONEMDSOONBAHRAMIMD CARRIE ANN R.CUSACKMDSENAIT W.DYSONMDMOLLY A.HINSHAWMDARNI K.KRISTJANSSONMD

Arch Dermatol. 2011;147(4):499-504. doi:10.1001/archdermatol.2011.63-b

Histopathologic examination revealed an unencapsulated, well-circumscribed, polypoid dermal tumor with nests and sheets of pale, eosinophilic, ovoid to spindled cells with relatively uniform, round to ovoid vesicular nuclei. Foci of myxoid stroma were present, and mature adipocytes were distributed throughout the lesion. Scattered regular mitotic figures were present, but cytologic atypia and pleomorphism were minimal. By immunohistochemistry, the majority of the lesional cells expressed S-100 protein, neuron-specific enolase, and epithelial membrane antigen. Smooth muscle actin and muscle-specific actin expression was also extensive. The cells were negative for melan-A, HMB45, CD34, various keratins, and glial fibrillary acidic protein. The lesion involved the deep margin of the biopsy specimen. Reexcision was recommended, but the patient did not return for follow-up.

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