We report a case of primary breast lymphoma in a 75-year-old woman who noticed a lump in her right breast after trauma. Mammographic, ultrasonographic, and pathologic correlations are provided. The typical appearance of primary breast lymphoma on mammography is a solitary, uncalcified, circumscribed, or indistinctly marginated mass with adjacent lymphadenopathy. On ultrasound, primary breast lymphoma is usually hypoechoic with circumscribed or microlobulated margins demonstrating increased vascularity. The differential diagnosis for a mass with this appearance is discussed in detail and includes hematoma, abscess, primary breast lymphoma, invasive ductal carcinoma, phyllodes tumor, and metastatic disease.