Fibrous histiocytoma of the tarsus: clinical and immunohistochemical observations with a differential diagnosis.

PURPOSE: To describe the diagnostic clinical findings and immunopathology of a fibrous histiocytoma of the upper eyelid tarsus of a 42-year-old man.

METHODS

Analysis of clinical features and results of histopathologic and immunohistochemical evaluations using antibodies against the biomarkers smooth muscle actin, S100, CD1a, CD3, CD20, CD31, CD34, CD68, CD163, factor XIIIa, adipophilin, androgen receptor, and Ki-67.

RESULTS

The skin moved over a firm lesion that was situated in the tarsus and protruded from the palpebral conjunctiva as a whitish flat-domed noninflamed mass that had caused an irritating corneal epitheliopathy. Histopathologically, there was a storiform or spiral nebular growth pattern, a moderate amount of intercellular collagen, and no nuclear atypia or mitotic activity. The main immunohistochemical findings were CD34 and smooth muscle actin negativity among the tumor cells and a scarcity of CD68/163 histiocytes. Androgen receptors were identified in the tumor cells.

CONCLUSIONS

CD34 histiocytoma of the tarsus is a rare, benign, and separate entity from a CD34 solitary fibrous tumor. Conservative tarsectomy is curative.