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.