Mammary fibromatosis: Case report

Clinical History

A middle-aged patient complaining of a palpable nodule in the upper inner quadrant of the right breast for three months. She denied previous diseases and family history of breast cancer.

Imaging Findings

Mammography revealed a dense and irregular nodule with indistinct contours in the upper inner quadrant of the right breast, in the posterior third, with measures of 2.9x2.7 cm. It was classified as a BI-RADS 4C.
On ultrasound, it presented as a solid, irregular and heterogeneous nodule, located in the upper inner quadrant of the right breast, seen at 2 o'clock position, measuring 2.8 x 2.0 x 1.2 cm and 5.0 cm distant from the nipple.
Doppler and elastography images were not performed.
A core biopsy guided by ultrasound was performed by removing 10 fragments. The result of the anatomopathological examination was of fusocellular proliferation presenting discrete nuclear atypia with rare mitoses.
The mammary magnetic resonance revealed hypointese nodule in T1 sequence that appeared heterogeneous in T2 due to bleeding after a core-biopsy procedure. The nodule presented restriction to diffusion, and had irregular contours. It was 0.9 cm distant from the pectoralis muscle.

Discussion

Background:
Mammary desmoid fibromatosis is a very rare locally aggressive benign neoplasm, accounting for about 0.2% of benign breast tumours. It originates from the fibroblasts and myofibroblasts of the breast parenchyma [1]. It was first described in 1832, and the name desmoid comes from the Greek desmos (tendon) [2]. It is derived from muscle-aponeurotic structures.
The aetiology of these lesions remains uncertain, but genetic mutations, trauma and hormonal factors have been mentioned as a possibility [3]. It has no predilection for age, family history or exposure factors, although certain cases occur after trauma [4].

Clinical Perspective:
It usually appears as a painless mass, always palpable and often mimicking cancer, and may also show retraction of the skin. The growth is slow and progressive and it can become very large. It may be adhered to the chest wall [5].
The lesion usually develops in one of the quadrants of the breast and the retroareolar location is uncommon [2].

Imaging Perspective:
The lesion appears on mammography generally as a spiculated mass, but may appear as an asymmetry, architectural distortion of the parenchyma or well-defined lobulated mass.
CT and MRI are also used to assess tissue infiltration of adjacent soft tissues, especially in patients who have previously been operated on the chest wall [1].
Fine needle aspiration has little diagnostic value because the material is generally insufficient.
Core biopsy or excisional biopsy is preferred for preoperative histologic diagnosis, but is not always diagnosed with mesenchymal tumours [1, 2].

Outcome:
The treatment of fibromatosis remains controversial because of the low incidence. However, the treatment of choice is currently wide local excision, but mastectomy may be required for extensive or locally recurrent disease, keeping in mind that it should be avoided when possible, especially in young women [1, 7].
Despite its benignity, it tends to invade and have local recurrence (21-27%) [6], presenting no potential for metastasis. When the lesion is adherent to fascia, muscle or skin, excision should be extended to include the affected area. There are reports of recurrence up to 11 years after surgery [7].
Conservative therapies (radiotheraphy, chemotherapy and hormonal therapy) should be considered when important neurovascular structures are involved or in case of a poor clinical status of the patient [7].

Teaching Points:
- Complaint of palpable mass in the breast should always be investigated.
- Rapidly growing breast nodule may correspond to desmoid fibromatosis.
- The desmoid tumour may invade adjacent soft tissues.

Differential Diagnosis List

Final Diagnosis

Mammary fibromatosis

URL:	https://eurorad.org/case/15406
DOI:	10.1594/EURORAD/CASE.15406
ISSN:	1563-4086