Malignant glomus tumor. A case report of widespread metastases in a patient with multiple glomus body hamartomas.

Glomus tumors are characteristically benign solitary tumors. A few cases of malignant glomus tumors have been reported; however, they are usually only locally invasive, and metastases are exceedingly rare. We report a case of widespread metastases of a malignant glomus tumor involving the skin, lungs, jejunum, liver, spleen, and lymph nodes in a 63-year-old man with end-stage chronic renal failure. At autopsy, multiple glomus body hamartomas were also noted throughout the dermis proximal to the skin tumors. Histologically, the tumor was composed of monotonous round cells in solid sheets and investing numerous capillary-sized vessels. Approximately four to six mitoses were present per high-power field. The tumor cells were strongly immunoreactive for actin and vimentin, and ultrastructurally there were whorls of microfilaments with focal condensations. This case is exceptional because of its aggressive course.