Basal-like Breast Cancer: Comparison of Imaging Characteristics

Background: Basal-like carcinoma is one of the breast subtypes that lacks expression of the estrogen receptor (ER), progesterone receptor (PR) and human epidermal growth factor receptor 2 (HER2). It has a poor prognosis and aggressive behavior. It is in a heterogeneous group with various other types of cancer, including metaplastic carcinoma, carcinomas with medullary features, medullary carcinoma, adenoid cystic carcinoma, secretory carcinoma, and invasive carcinoma arising in the setting of BRCA1 mutations. Imaging features of basal-like cancers have not been uniform, and there are no studies with imaging comparisons between basal-like carcinomas. Objectives: To compare imaging features of basal-like carcinomas and to understand their characteristics. Methods: By using our radiologic database, we retrospectively searched 37 cases of metaplastic carcinoma and 44 cases of invasive carcinoma with medullary features (ICMF). Two radiologists reviewed images according to ACR BI-RADS lexicon. Results: The higher Ki-67 and absence of calcifications were statistically significant in ICMF than in metaplastic carcinoma. Metaplastic carcinoma demonstrated oval shape and parallel orientation more frequently. ICMF showed more irregular shape and angular margin on ultrasound, irregular or spiculated margin on breast MRI. ICMF showed more delayed washout pattern of enhancement than metaplastic carcinoma. Intratumoral T2, a very high signal was noted more in metaplastic carcinoma. Conclusion: Our study presents variable imaging features observed between basal-like carcinomas. Although it is not sufficient to predict clinical progress, aggressiveness or prognosis of basal-like carcinomas, the results of this study will be helpful in understanding and diagnosing various basallike carcinomas.