Glomus tumor: a clinicopathologic and electron microscopic study.

This clinicopathologic study concerns 63 instances of glomus tumor of the soft tissues. The tumors occurred at different ages but were more common in earlier adult life and most commonly occurred on the fingers (35 cases), frequently as subungual nodules (26 cases). Other sites of occurrence were the forearm in seven, the knee in seven, and the leg in six. All patients but one complained of pain. Histologically, the tumors, showing endothelium-lined vascular spaces surrounded by masses of epithelioid cells, could be divided into three varieties: vascular (29 cases), myxoid (23 cases), and solid (11 cases). Under electron microscope the tumor cells in four cases proved to be smooth-muscle cells. The clinicopathologic evidence presented supports the hypothesis that the glomus tumor is a tumor-like lesion of mesodermal disorder rather than a true neoplasm.