Desmoid Fibromatosis of Breast Resembling Carcinoma: A Diagnostic Conundrum

A BSTRACT Desmoid fibromatosis of the breast is an uncommon, benign, and locally invasive fibroblastic tumor that may show signs of malignancy but cannot spread. The etiology is unknown, whereas physical, hormonal, and genetic factors significantly impact how quickly it grows. Patients primarily in their fourth and fifth decades of life are affected by this entity. Its clinical and radiological resemblance to carcinoma can pose a diagnostic challenge. Surgical resection and subsequent histopathological examination confirmed the diagnosis of desmoid fibromatosis. We present a case of a 45-year-old female with a hard, tender, and irregular mass measuring 4 cm in the upper outer quadrant of her left breast that mimicked carcinoma in imaging studies as well as clinically. The breast ultrasound was suggestive of a left breast lesion of BIRADS IV. The left breast’s full field digital mammography showed a mixed fibro glandular pattern of type C, which could be obscuring the small lesion. The patient underwent surgical resection of the mass with wide margins, which was sent for histopathological examination. On histopathological examination, a diagnosis of desmoid fibromatosis was made. This case report underscores the importance of considering desmoid fibromatosis in the differential diagnosis of suspicious masses to avoid unnecessary aggressive treatments and emphasizes the significance of an accurate diagnosis. A thorough histopathological examination, along with immunohistochemistry, plays a crucial role in the diagnosis of this entity.