Nuchal-type fibromas or nuchal fibromas are rare benign fibrous tumours arising from the connective tissues of the neck.
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Terminology
The term 'collagenosis nuchae' is now discouraged 1.
Epidemiology
Nuchal-type fibromas are rare tumours and are mainly found in men in their 30s and 40s 1.
Associations
Approximately half of the patients with the condition also have diabetes mellitus 1.
Diagnosis
The diagnosis of nuchal-type fibroma is established by pathology and location 1.
Diagnostic criteria
Diagnostic criteria according to the WHO classification of tumours: soft tissue and bone (5th edition) 1:
- hypocellular collagenous lesion often with tiny nerve bundles
- typically found in the neck
- bland CD34 positive spindle cells
Clinical presentation
Nuchal-type fibromas usually present as slowly growing indolent masses 1-4.
Pathology
Nuchal-type fibromas are paucicellular collagenous tumours made of spindle cells with entrapped small nerve bundles similar to traumatic neuromas 1.
Aetiology
The aetiology of nuchal type fibroma is unknown 1.
Location
The typical location is the subcutaneous tissues of the posterior neck. They can also arise from the upper back but have also been seen in the shoulder face and the extremities 1-3.
Macroscopic appearance
Nuchal-type fibromas are ill-defined tumours of firm consistency and usually white colour 1,4.
Microscopic appearance
Microscopically nuchal fibromas show the following features 1-3:
- thick unorganized composition of collagen fibres with more delicate elastic fibres
- few bland spindle fibroblasts
- entrapped small peripheral nerves and adipose tissue
- extension into the underlying skeletal muscle
Immunophenotype
Immunohistochemistry stains usually express CD34 in are negative for β-catenin 1,2.
Radiographic features
Ultrasound
Ultrasound findings have been described as hypoechoic 2.
MRI
Nuchal-type fibromas can be well-circumscribed or ill-defined lesions mostly found in the superficial soft tissues 2-5.
Signal characteristics
- T1: usually low signal intensity (rarely mixed or high signal)
- T2: low to mixed-signal intensity
- STIR: usually low signal intensity
- T1 C+ (Gd): avid enhancement
Radiology report
The radiological report should include a description of the following:
- location and size of the tumour
- relation to the muscular fascia
- relation to the spinous processes
Treatment and prognosis
Nuchal-type fibromas are benign tumours. Local recurrence can happen after excision, but they do not metastasise 1,2.
History and etymology
The first description of nuchal fibroma was made by the Austrian-American pathologist Franz Michael Enzinger and the American pathologist Sharon Ann Whelan Weiss in 1988 2.
The Terminologia Anatomica refers to the neck as a whole as the "collum". In official Latin anatomical nomenclature, "cervix" refers to the front of the neck and "nucha" to the back (nape) of the neck 6.
Differential diagnosis
The differential diagnosis of nuchal type fibroma includes the following 1,2:
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