Intravenous glomus tumor of the forearm.

An intravenous glomus tumor occurring in a forearm vein is reported. The patient had a painful subcutaneous mass which was completely excised. This mass was a neoplasm which expanded the lumen of a vein and extended throughout its wall into the surrounding subcutaneous fat. The neoplasm consisted of sheets of rounded cells with a capillary stroma. The neoplastic cells were closely apposed to the capillary vessels and were positive for vimentin, smooth muscle actin and muscle specific actin. The cells were negative for desmin, factor VIII-related antigen, epithelial membrane antigen, cytokeratins, S-100 protein and chromogranin. This is the 2nd reported case of intravenous glomus tumor of the forearm. This unusual presentation may be due to intravascular extension by a cutaneous glomus tumor. The potential for intravascular growth by glomus tumor should be recognized by surgeons, dermatologists and pathologists.