The glomus coccygeum or glomus body of the coccyx is a microanatomical structure formed by an arteriovenous anastomosis and represents likely a phylogenetic vestigial structure 1.
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Gross anatomy
Glomus bodies are spheroidal or ovoid well-circumscribed vascular lesions. Their size is usually up to 5 mm in dimensions 1,2.
Relations
They are usually located in the soft tissue immediately ventral or below the tip of the coccyx near the anococcygeal ligament 1,2.
Histology
Each glomus body consists of up to four arterial segments and branches into arterioles, that are surrounded by layers of modified smooth muscle cells and drain into a collecting venous plexus 1.
Immunophenotype
Glomus cells usually express smooth muscle actin, vimentin, and neuron-specific enolase 1,2.
Variant anatomy
The actual prevalence of glomus coccygeum is unclear, but they seem to be quite common and were found in >30% of the coccygectomy specimens in anatomic studies 1-4.
Radiographic features
Due to their small size glomus bodies should not be noticeable in most radiographic studies including MRI 3.
History and etymology
The glomus coccygeum was first identified by Hubert von Luschka 5 (1820-1875), who compared it to the glomus caroticum. Its vascular origin was first recognized by Julius Arnold (1835-1915), but it was not until 1942 when William H. Hollinshead established physiological and anatomical discriminations between the coccygeal glomus tumor and the glomus caroticum.
Related pathology
Very few cases of real benign parargnaglioma of the coccyx have been reported in the literature. Those tumors were larger, however, exhibited an expansile growth and patients had symptoms of coccygodynia, tenderness and sensitivity to cold similar to peripheral glomangiomas.
They represent a significant challenge for most pathologists 1,2.
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