Coccygeal glomus tumours are rare benign neoplasms with the same morphologic features, expressed by glomangiomas occurring at extra coccygeal sites as under the fingernails or toes.
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Terminology
The term "glomus" was historically used to describe certain types of neuroendocrine tumours arising from paraganglia. The term is, however, imprecise and can be confused with the glomus bodies and tumours that arise from them. It can also be mixed up with glomus tumours of the subcutaneous skin, also referred to as glomangioma.
The glomus tumour of the coccyx is often put on a level with the ‘glomus body of the coccyx’ or ‘glomus coccygeum', which is seen as a normal anatomic variant 1,2
Epidemiology
It seems to be a rather rarely described entity with only a few cases described in the literature 1-3.
Clinical presentation
Patients complain of coccygodynia, thus pain, tenderness and sensitivity to cold 1-3 as described with peripheral extracoccygeal glomangiomas.
Pathology
Benign glomangiomas are expansile, well-circumscribed vascular lesions, which can erode the bone surface. Their size is usually up to 1-2 cm in dimensions 1,2 and thus larger than the usual size of the glomus coccygeum, which is reported 1-5 mm 2. Similar to the glomus coccygeum, coccygeal glomus tumours seem to be located in the soft tissue immediately ventral or below to the tip of the coccyx near the anococcygeal ligament 1-3.
Macroscopic appearance
The macroscopic appearance of coccygeal glomus tumours is that of a well-circumscribed nodular lesion 1,2.
Microscopic appearance
Microscopically they consist of small arterioles, surrounded by several layers of modified smooth muscle cells.
Immunophenotype
Glomus cells usually express smooth muscle actin, vimentin and neurone specific enolase 1,2.
Radiographic features
Plain radiograph
Glomus tumours of the coccyx are usually quite small and will usually not be noticed on plain radiographs.
CT
There are no reports about the appearance of coccygeal glomangiomas in the literature. However, it should look like an ovoid well-circumscribed lesion with soft tissue density, with possible bone erosion ref.
MRI
A report describes the lesion at the coccyx as an ovoid lesion with well-circumscribed margins 1:
T1: hypointense
T2: hyperintense
T1 C+ (Gd): homogeneous avid enhancement
Radiology report
The radiological report should include a description of the following:
location, size and signal characteristics of the lesion
form, margins and transition zone
bony erosions
any other abnormalities of the coccyx and the sacrum as well as the pelvic floor, which might be a source for the patient's pain or symptoms
Treatment and prognosis
In case of longstanding otherwise non-explained coccygodynia, it can be excised.
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 recognised by Julius Arnold (1835-1915), but it was not until 1942 when William H. Hollinshead established physiological and anatomical discriminations between the glomus coccygeum and the glomus caroticum.
Coccygeal glomus tumours have been reported by Nutz and Stelzner 3, Llombart 4 and Kim 1.
Differential diagnosis
The differential diagnosis of tumours arising from the coccygeal glomus includes the following 2:
glomus coccygeum: smaller, frequent should not cause cold sensitivity or tenderness
paraganglion or paraganglioma
Practical points
Coccygeal paraganglioma represent a significant challenge for most pathologists 2, therefore it might be advisable to point out the suspected diagnosis in the radiological report.
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