Glomus coccygeum in surgical pathology specimens: small troublemaker.

Abstract

Rarely encountered nonpathologic structures may pose diagnostic problems and cause unnecessary special investigations. More importantly, however, they may be falsely accused as culprits in unrelated pathologic processes. Glomus coccygeum is one such structure. Glomus bodies (including coccygeal glomus) consist of modified smooth muscle cells arranged in layers around small vascular channels. When found in distal extremities, they generally do not represent a diagnostic problem; however, large glomus bodies present in a pericoccygeal location (glomus coccygeum) may cause significant problems for a surgical pathologist unfamiliar with this structure. We reviewed 37 coccygeal bones removed during rectal resection for carcinoma (rectal and uterine) and for various other reasons, among which was a single case of coccygodynia. Immunohistochemical and ultrastructural examinations were performed in selected cases. Sharply circumscribed glomus bodies composed of various proportions of glomus cells without atypia or pleomorphism and without expansile growth or infiltration of surrounding soft tissue or bone were identified in 50% of cases. Size varied significantly (maximum 4 mm), but paradoxically the smallest glomus body (less than 1 mm) was found in the case of coccygodynia. Glomus coccygeum posed a significant diagnostic challenge to the pathologists involved in these cases, as the retrospective review found that it was diagnosed correctly in only 3 cases. Glomus coccygeum is a nonpathologic structure that exhibits significant variation in size and proportion of the constitutive elements. Immunohistochemical demonstration of smooth muscle actin and neuron-specific enolase in glomus cells may be beneficial for accurate identification of this organelle.