Overdiagnosis of medullary carcinoma: a mammographic-pathologic correlative study.

PURPOSE: To evaluate the mammographic features of medullary carcinoma, to determine the frequency of pathologic overdiagnosis of this neoplasm, and to assess whether mammography can distinguish true from atypical medullary carcinomas, since this distinction has important prognostic implications. MATERIALS AND METHODS: Retrospective review revealed 25 patients with an initial pathologic diagnosis of medullary carcinoma. Histopathologic slides and mammograms were reviewed. RESULTS: After review of histopathologic slides, 14 (56%) lesions were classified as medullary carcinomas and 11 (44%) as atypical medullary carcinomas. At mammography, a circumscribed mass was present in four of the 14 (28%) medullary carcinomas and in one of the 11 (9%) atypical medullary carcinomas (P = .34), an indistinct mass was present in seven of the 14 (50%) medullary carcinomas and in five of the 11 (45%) atypical medullary carcinomas (P = .86), and an obscured mass was present in two of the 14 (14%) medullary carcinomas and in three of the 11 (27%) atypical medullary carcinomas (P = .62). Calcification, which was present in one of the 11 (9%) atypical medullary carcinomas, and s spiculated border, which was present in one of the 11 (9%) atypical medullary carcinomas, were not observed in medullary carcinomas (P = .44). CONCLUSION: At mammography, medullary carcinoma was usually an uncalcified mass with indistinct or circumscribed borders. Atypical medullary carcinoma may be misdiagnosed as medullary carcinoma. Mammography could not reliably help distinguish true medullary carcinomas from atypical medullary carcinomas.