Immunophenotypic analysis of glomus coccygeum associated with coccygodynia.

OBJECTIVE: Glomus coccygeum is a glomus body which is found in the pericoccygeal soft tissue. This specialised arteriovenous anastomosis is a non-pathological vestigial structure usually larger than its equivalent in the distal extremities. Its prevalence is uncertain. Glomus coccygeum has been associated with coccygodynia and can cause diagnostic problems to pathologists unfamiliar with this entity. MATERIALS AND METHODS: The presence of a glomus coccygeum was sought in 40 coccygectomy specimens and correlated with clinical, radiological and histological findings. RESULTS: A glomus coccygeum was identified in 13 samples (35%). Glomus cells expressed smooth muscle actin (SMA) and were negative for desmin, S100, cytokeratin and a wide range of vascular markers. Proliferative activity was low. Pre-operative MRI did not identify these tiny lesions, and most patients with coccygodynia did not have a glomus coccygeum. CONCLUSION: Glomus coccygeum is a common microanatomical structure which can be distinguished from glomus and other tumours by its small size, SMA expression and low proliferative activity.