Pericytoma (Glomus Type)

In 1923 Zimmermann 1 a Swiss histologist, first described the pericyte, a pericapillary modified smooth muscle cell with dendritic processes which encircle capillaries and is believed to exert a contractile effect in regulating the capillary lumen. Subsequently Murray and Stout 2,3 demonstrated that 2 known vascular tumors, hemangiopericytomas and glomus tumors, could be classified as pericytomas since they were both characterized by abnormal proliferation of Zimmermann's pericyte. Inasmuch as the pericyte is common to both tumors, differentiation is often possible only by differences in morphologic architecture. The glomus tumor is characterized by, and derives its name from, its structural similarity to the neuromyoarterial glomus, a normal, subungual anatomical vascular complex which circumvents capillaries by allowing direct arteriovenous shunts. In hemangiopericytoma the pericyte proliferates in no such recognizable "organoid" pattern. These tumors are well documented for all age groups, in case reports and collected series in the adult literature. However, since neither glomus