[Epithelioid cell histiocytoma]

We report on seven examples of this rare, only recently described benign tumor, which presented clinically as solitary elevated nodules on the lower (n = 5) and upper (n = 2) extremity, measuring between 0.6 and 1.1 cm in diameter. Histologically, all tumors were well-defined with a characteristic epidermal collarette. There were abundant (60-80%) epithelioid cells with prominent cytoplasm, a vesicular nucleus and inconspicuous nucleolus, as well as a number of dilated blood vessels. Immunohistologically, tumor cells did not react with monocyte/macrophage antibodies (KP1, MAC387). In addition, there was no evidence of myofibroblastic differentiation (alpha-smooth muscle actin and desmin negative). Thus, while immunohistological markers are helpful to exclude the diagnosis of other tumors, they do not shed light on the differentiation of epithelioid cell histiocytomas. The present cases are identical to those described originally. Recently similar lesions have been described in deeper parts of the corium as well as more cellular forms. Epithelioid cell histiocytoma represents a characteristic, poorly known variant within the spectrum of benign fibrous histiocytomas; it needs to be distinguished clinically and histopathologically especially from Spitz nevus.