A 70-yr-old man presented with a slightly hyperpigmented nodule on his hand that had been growing slowly for the past 3-4 mo. It was not painful and he was otherwise in good health. The nodule was firm and had no overlying surface changes. The clinical differential diagnosis included dermatofibroma, dermatofibrosarcoma protuberans, Kaposi's sarcoma and a foreign body giant cell granulomatous reaction. A biopsy was performed and is represented in Fig. 5A,B.
The histologic differential diagnosis included mainly Kaposi's sarcoma, based upon the extravasation of erythrocytes, and dermatofi-brosarcoma protuberans, based upon the dense cellularity with minimal pleomorphism or cytologic atypia. Also considered were spindle cell melanoma and a solitary fibrous tumor (which was thought to be extremely unlikely). An immunostaining panel was developed to resolve this diagnostic dilemma and is shown in Table 3.
As is seen in Fig. 6A,B, the tumor cells stained strongly with both anti-CD34 and anti-CD31. They failed to express S100 protein (not
Differential Diagnosis to Dermal Spindle Cell Neoplasm
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