<prompt> A 27-year-old woman in the third trimester of her third pregnancy discovers a lump in her left breast. On physical examination, a 2-cm, discrete, freely movable mass beneath the nipple is palpable. After the birth of a term infant, the mass appears to decrease in size. The infant is breastfed without difficulty. What is the most likely diagnosis?FibroadenomaIntraductal papillomaLobular carcinoma in situMedullary carcinoma  <response>: Fibroadenomas are common and may enlarge during pregnancy or late in each menstrual cycle. Most intraductal papillomas are smaller than 1 cm and are not influenced by hormonal changes. Lobular carcinoma in situ is typically an ill-defined lesion without a mass effect. Medullary carcinomas tend to be large; they account for only about 1 of all breast carcinomas. Phyllodes tumors are uncommon and tend to be larger than 4 cm. 