Angiomatoid fibrous histiocytoma: first report of primary pulmonary origin

Angiomatoid fibrous histiocytoma is an uncommon soft tissue tumor most frequently affecting the deep dermis and subcutis of the extremities in children and young adults. We report the first case presenting as a primary pulmonary tumor in a 46-year-old man. Histologically, the tumor was composed of multiple cellular nodules surrounded by a fibrous pseudocapsule and peritumoral lymphoplasmacytic infiltrates. The nodules were composed of histiocytoid cells with a diffuse, whorled, or vague storiform pattern, with the intervening areas densely packed with plasma cells and lymphocytes. The tumor cells were immunoreactive for epithelial membrane antigen, and focally desmin, CD68, and CD163. Fluorescence in-situ hybridization revealed EWS gene translocation, which was further confirmed on polymerase chain reaction to result from EWS/ATF1 gene fusion. It is important to recognize that angiomatoid fibrous histiocytoma can occur in the lung because its histologic features are rather nondescript and thus can be mistaken for other tumors such as meningioma, inflammatory myofibroblastic tumor, and follicular dendritic cell sarcoma.