This chapter covers glomus tumor and related entities: sinonasal hemangiopericytoma and myopericytoma. These tumors are sometimes classified as perivascular tumors. The term glomus tumor has historically also been applied to jugulotympanic paragangliomas (glomus jugulare, glomus tympanicum); however, paraganglioma is the proper designation for these tumors. Hemangiopericytoma of soft tissues, which is thought to be closely related to solitary fibrous tumor, is discussed in Chapter 12.

GLOMUS TUMOR

A glomus tumor shows mesenchymal differentiation similar to the specialized smooth muscle cells of the glomus bodies that regulate peripheral blood flow. Most glomus tumors are benign, but rare atypical and malignant examples exist.

Glomus Bodies

Normal glomus bodies are present in the distal extremities, such as fingers, and other acral locations, but they are detected infrequently because of their small size. Perhaps the most common location to encounter normal glomus bodies is the coccygeal area, where small clusters of glomus cells are located ventral to the tip of coccyx. In one study, these bodies were detected in 18 of 37 coccygectomy specimens, and another study revealed 2 glomus bodies in 2 of 382 excisions of pilonidal sinus (0.5%). The author and colleagues have also encountered glomus bodies in a wall of a tailgut cyst (Fig. 23.1), and such an instance has been reported at least once.

The glomus cell clusters in the coccygeal region can be present in an area of several millimeters in diameter, and in some cases the distinction from a small glomus tumor can become arbitrary, especially if larger solid clusters of glomus cells are present.