Medullary Carcinoma of the Breast: Sonographic Features Distinguishing it from Fibroadenoma

This study was undertaken to compare the sonographic findings of medullary carcinoma with those of fibroadenoma and to determine the sonographic features that are helpful in differentiating medullary carcinoma from fibroadenoma. We retrospectively compared 16 typical medullary carcinomas and 45 consecutive fibroadenomas, recording size, length to anteroposterior diameter (L/AP) ratio, shape, margin, wall thickness, internal echo pattern, posterior sound transmission and enlargement of axillary lymph nodes. Medullary carcinomas were larger (p = 0.0019) and taller (p = 0.0048) than fibroadenomas. Round (4/16, 25%) or lobular (5/16, 31%) shapes for medullary carcinoma were more common than in fibroadenomas (0/45, 12/45) (p = 0.0012). A focally thick wall (10/16, 63%) was more common in medullary carcinoma than in fibroadenoma (1/45, 2%) (p = 0.00001). Anechoic cystic space was more common in medullary carcinoma (6/16, 38%) than in fibroadenoma (1/45, 2%) (p = 0.0026). Enlarged axillary lymph nodes were more common in patients with medullary carcinoma (7/16, 44%) than in patients with fibroadenoma (2/45, 4%). On sonography, larger masses with a greater L/AP ratio, which are round or lobular in shape, with a focally thick wall and anechoic cystic space, and enlarged axillary lymph nodes are more common findings in patients with medullary carcinoma than in patients with fibroadenoma. These sonographic findings help to differentiate medullary carcinoma from fibroadenoma.