A 30-year-old woman suffers traumatic injury to her breast while playing soccer. Physical examination reveals a 3-cm area of ecchymosis on the left breast. Two weeks later, the patient palpates a firm lump beneath the area where the bruise had been located. Which of the following is the most likely pathologic diagnosis?

A history of trauma can usually be elicited in cases of fat necrosis occurring in the breast. Initially, the lesion consists of necrosis of adipocytes and hemorrhage, after which phagocytic cells remove the lipid debris. Fibroblastic proliferation during healing leads to fingers of fibrous scar tissue that extend into the adjacent breast tissue. As a result, an irregular, fixed, hard mass may ensue and clinically resemble breast cancer. Dystrophic calcification, a common feature of breast cancer, may also be detected radiographically in areas of fat necrosis. Thus, the lesions often require biopsy to establish their benign character. The other choices are not associated with trauma.Diagnosis: Fat necrosis of the breast