Imaging findings of a biopsy-proven desmoid tumor of the axilla in a young female

Desmoid tumors (fibromatoses) are rare but locally aggressive tumors that do not metastasize. They are non-encapsulated, well-differentiated lesions made of fibroblasts and collagen, which mainly appear in the mesentery and abdominal wall. Rarely, these tumors can also occur in breasts, making up approximately 0.2% of all breast neoplasms. Treatment typically includes surgical excision and/or medical management. We describe a case of a 31-year-old female presenting with a mass in her left axilla that was biopsy proven to be a desmoid tumor. In this case report, we discuss the various imaging findings present on ultrasound, mammography, computed tomography, and magnetic resonance imaging.