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A 41-year-old woman has felt a large breast lump that has increased slowly in size for the past 3 years. On physical examination there is a 9 cm firm, movable mass present in her left breast. The overlying skin appears normal; there is no axillary lymphadenopathy. The mass is excised and grossly appears soft and fleshy. On microscopic examination this mass has a lymphoid stroma with little fibrosis surrounding sheets of large vesicular cells with frequent mitoses. Which of the following is the most likely diagnosis?

A Infiltrating ductal carcinoma

B Colloid carcinoma

C Medullary carcinoma

D Lobular carcinoma

E Phyllodes tumor

F Diffuse large B cell lymphoma

C seems appropriate.

cc

AAA

Medullary carcinoma is often bulky, with pushing margins. It lacks the desmoplasia typical of ductal carcinomas. It accounts for only about 1% of breast cancers.