A 46-YEAR-OLD previously healthy woman was seen for a rapidly enlarging right breast mass. She had been told many years before that she had a right breast "cyst," and the size had evidently not changed until the past 8 to 12 weeks. The patient denied a history of familial breast disease, left breast disease, or nipple discharge. Physical examination demonstrated venous engorgement in the skin of the right breast and a 15 × 10-cm firm, nontender, movable mass (Figure 1). There were no other skin changes, no fixation to the chest wall, and no palpable axillary nodes. Fine-needle aspiration of the right breast mass demonstrated multiple fragments of stroma with marked atypia.