Imaging Differences in Metaplastic and Invasive Ductal Carcinomas of the Breast

OBJECTIVE: The purpose of this study was to compare the imaging features of metaplastic breast carcinoma with those of invasive ductal carcinoma. MATERIALS AND METHODS: Women diagnosed on preoperative mammography or sonography with metaplastic breast carcinoma and T-stage matched invasive ductal carcinoma of the breast from a single pathology database were included in the study. Clinical and pathologic information on all metaplastic cancers was documented. Mammography and sonography variables were recorded using the BI-RADS lexicon. Groups were compared using Fisher's exact test, the chi-square test, or Wilcoxon's rank sum test, as appropriate. RESULTS: Forty-three patients diagnosed with metaplastic carcinoma were matched to 43 patients with ductal carcinoma by tumor T stage. Patients with metaplastic carcinoma were younger (median, 46 vs 53 years, p = 0.048) than those with ductal carcinoma. Mammographically, metaplastic carcinomas were less frequently irregular in shape (16% vs 74%, p < 0.0001) and less frequently showed microlobulated or spiculated margins (19% vs 56%, p = 0.0008) and calcifications (25% vs 51%, p = 0.02) when compared with ductal carcinomas. Sonographically, metaplastic carcinomas were less frequently irregular in shape (27% vs 69%, p = 0.001) and less frequently showed angular margins (9% vs 49%) and posterior acoustic shadowing (9% vs 49%, p < 0.0001). CONCLUSION: Characteristic malignant imaging features, including irregular shape, spiculated margins, segmentally distributed pleomorphic calcifications, and posterior acoustic shadowing, are uncommon in metaplastic carcinomas. These carcinomas tend to show more benign imaging features, such as round or oval shape with circumscribed margins, when compared with ductal carcinomas.