Breast Fibromatosis: A Radiologist’s Perspective

A 39-year-old woman with a previous history of right-breast mastectomy, radiation, chemotherapy, and reconstruction for multifocal invasive ductal carcinoma 3 years prior and left lateral breast benign lumpectomy for fibroadenoma remotely presented with a new palpable lump in the lower outer quadrant of her left breast. On the clinical exam, a firm lump fixed to the chest wall was palpated in the lower outer quadrant of the left breast. On mammography, due to the very posterior location of the mass felt clinically, no mammographic correlation was appreciated, even with tomosynthesis and an exaggerated craniocaudal view (Figure 1). Left breast mammogram in a 39-year-old woman with a history of right breast mastectomy with reconstruction and left breast benign lumpectomy remotely. (A) Mediolateral oblique and (B) craniocaudal views demonstrate a long-standing stable circumscribed mass with coarse calcifications in the lateral central breast corresponding to a known fibroadenoma (solid arrow). Due to the very posterior location of the mass felt clinically, no mammographic correlation is appreciated. On US, an irregularly shaped mass with poorly defined borders and internal vascularity measuring up to 2.9 cm was found at 4 o’clock, 5 cm from the nipple (Figure 2). Targeted left-breast US in a 39-year-old woman with a history of right-breast mastectomy with reconstruction and left-breast benign lumpectomy remotely. Grayscale (A) and color (B) Doppler reveal an irregularly shaped mass (arrows) with poorly defined margins, internal vascularity, and significant posterior shadowing at the 4 o’clock position, 5 cm from the nipple. On MRI, an irregular shape, spiculated-margins mass with strong enhancement and persistent enhancement kinetics was seen. The mass invaded the inferior aspect of the pectoralis muscle (Figure 3). Breast MRI in a 39-year-old woman with a history of right-breast mastectomy with reconstruction and left-breast benign lumpectomy remotely. T1 fat-suppressed contrast-enhanced subtracted sagittal (A), T1 fat-suppressed contrast-enhanced nonsubtracted sagittal (B), and T1 fat-suppressed contrast-enhanced subtracted axial (C) images show a spiculated, irregular mass (solid arrows) with substantial enhancement in the lower outer quadrant of the left breast. The mass invades the inferior end of the pectoralis muscle, which shows abnormal enhancement (dashed arrows). The abnormal enhancement abuts the ribs and intercostal muscles, but no indication of involvement within the ribs exists. Additionally, there are no signs of overlying skin involvement. Signs of mastectomy and reconstruction are also noted in the right breast. The US-guided core needle biopsy revealed a spindle cell lesion with some mitotic activity. Differential diagnoses of metaplastic carcinoma and mesenchymal neoplasms were suggested without ruling out sarcoma. Subsequently, the pathology was reviewed at the sarcoma clinic and discussed at the tumor board, which confirmed a diagnosis of fibromatosis. Fibromatosis tumor of the breast is a rare condition with a variable spectrum ranging from a locally limited lesion to an aggressive, destructive one. The terms fibromatosis, desmoid tumor, and aggressive fibromatosis are often used interchangeably. The etiology of this tumor is unknown; however, it most often affects women during their childbearing age after a trauma or different surgical procedures of the breast. Other suggested risk factors are augmentation mammoplasty with saline or silicone, oral contraceptive pills, chemotherapy, familial adenomatous polyposis syndrome, and Gardner syndrome. This case occurred in childbearing age with a prior history of surgery in the same breast and chemotherapy. Fibromatosis tumor cannot be differentiated from breast carcinoma clinically or by breast imaging. However, imaging has a significant role in detecting and planning treatment and follow-up. On breast imaging, fibromatosis typically appears as an irregularly shaped, noncalcified, high-density mass with a spiculated border, such as our case. The histopathologic differential diagnosis includes reactive processes (scar or biopsy-site reaction), nodular fasciitis, metaplastic carcinoma, and spindle cell–type low-grade fibrosarcoma. The hallmark of histological diagnosis of fibromatosis is the proliferation of the bland-looking spindle cells. Immunohistochemical cytokeratin staining helps rule out carcinoma. In malignant fibrosarcoma, marked cytologic pleomorphism and increased mitotic activity are notable. Breast fibromatosis treatment varies from inflammatory drugs, tyrosine kinase inhibitors, chemotherapy, and radiation to surgical excision. Recent management of fibromatosis has shifted toward nonsurgical options rather than surgery, which was the standard of care in the past. Complete excision can be challenging and require chest wall reconstruction. There is a high rate of local recurrence following surgical excision, reported between 24% and 77% over a 10-year period. None declared. None declared. Afsaneh Alikhassi (Conceptualization, Data curation, Investigation, Supervision, Validation, Visualization, Writing - original draft, Writing - review & editing) and Mia Skarpathiotakis (Conceptualization, Validation, Writing - review & editing)

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