Fine structure of the human coccygeal body: a light and electron microscopic study

There is only limited data on the microscopic structure of the coccygeal body in classical textbooks. Although there are several articles describing the light microscopic structure of the organ, the data presented are rather conflicting especially when comparing glomus tumors and normal coccygeal bodies. We therefore examined the pericoccygeal soft tissues histologically with the aim of obtaining further evidence. At the light microscopic examination, coccygeal bodies were distinguished as sections of several blood vessels encapsulated by a connective tissue capsule. Small arteries within the coccygeal bodies had an unusual endothelial lining, resembling pseudostratified epithelium or neuro-epithelium. We observed increased numbers of glomus cells in a few samples. A highly tortuous course run by the small arteries was observed in the serial sections. At their electron microscopic examination, endothelial cells exhibited the features of columnar epithelial cells, though some appeared to be vacuole rich. The basal surface of the cells showed basal infoldings, but not as extensive as those of absorptive cells. External lamina, subplasmalemmal vesicles, bundles of microfilaments, groups of membrane bound organelles including mitochondria and endoplasmic reticulum were observed in glomus cells. In conclusion, it is rather difficult to use the term tumor for the coccygeal bodies when relying solely on the number of cells observed, because some segments of the coccygeal bodies were rich in glomus cells. It is more likely that the coccygeal bodies show variability in different individuals. The characteristics of the endothelium of the small arteries in coccygeal bodies needs to be examined in a wider range of specimens in order to be validated as a unique entity.