Fibromatosis of the breast

Fibromatosis of the breast (also known as an extra-abdominal desmoid tumour of the breast or mammary fibromatosis ⁴) is considered as a type of rare breast tumour. It is a non-metastasising benign but locally invasive stromal tumour ⁴. However, it can mimic more sinister types of breast cancer on both imaging and clinical findings ⁸.

Epidemiology

They account for only 0.2% of all breast tumours ⁹.

Clinical presentation

A desmoid tumour appears as a solitary, hard and painless nodule, which sometimes can be attached to the skin or to the pectoral muscle fascia.

Pathology

The entity is pathologically indistinguishable from fibromatosis occurring elsewhere in the body. The tumour has a with a fibroblastic and myofibroblastic origin.

Associations

Recognised associations include:

• Gardner syndrome ^4,9
• saline or silicone breast implants^4,9
• prior surgical trauma ^4,9

Location

• while it can occur anywhere in the breast, lesions may tend to occur in close proximity to pectoral muscles

Radiographic features

Mammography

A spiculated, irregular, non-calcified mass is considered the most common mammographic finding.

Breast ultrasound

Fibromatosis typically appears as a solid, spiculated or microlobulated, irregular hypoechoic mass with straightening and tethering of Cooper ligaments, which is very difficult to differentiate from a malignant lesion.

Breast MRI

Usually seen as an irregular breast mass.

• T1: mammary fibromatosis may appear as ill-defined, hypo- to isointense masses
• T2: usually heterogeneously hyperintense in signal
• T1 C+ (Gd): often show suspicious, slow enhancement after contrast administration 

MRI is often useful to show chest wall involvement in selected cases prior to surgical planning.

Treatment and prognosis

Although it is a benign non-metastasising tumour, it can be locally aggressive. Wide local excision with clear margins remains the treatment of choice ⁵. Recurrence rates can be high, especially in those with positive margins. Recurrence is less likely if a wide excision is performed and resection margins are made sure to be disease-free. Recurrences are also often treated with radical excision, aslike the primary tumour.

See also

• desmoid tumour