Nuchal type fibroma

Nuchal-type fibromas or nuchal fibromas are rare benign fibrous tumors arising from the connective tissues of the neck.

Terminology

The term 'collagenosis nuchae' is now discouraged ¹.

Epidemiology

Nuchal-type fibromas are rare tumors 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 tumors: soft tissue and bone (5^th 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 tumors made of spindle cells with entrapped small nerve bundles similar to traumatic neuromas ¹.

Etiology

The etiology 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 tumors of firm consistency and usually white color ^1,4.

Microscopic appearance

Microscopically nuchal fibromas show the following  features ^1-3:

• thick unorganized composition of collagen fibers with more delicate elastic fibers
• 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 tumor
• relation to the muscular fascia
• relation to the spinous processes

Treatment and prognosis

Nuchal-type fibromas are benign tumors. Local recurrence can happen after excision, but they do not metastasize ^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:

• elastofibroma
• fibromatosis
• Gardner fibroma
• solitary fibrous tumor