To evaluate the value of preoperative residual breast calcifications in predicting residual tumor after neoadjuvant chemotherapy (NAC).

A retrospective study was conducted on breast cancer patients who received NAC from January 2020 to December 2024 and showed suspicious microcalcifications within or near the tumor bed on mammography. Residual microcalcifications and residual lesions were analyzed by magnetic resonance imaging (MRI), and correlated with histopathological findings of residual tumors and immunohistochemical markers. Statistical analysis was performed using SPSS 28.0, with Fisher's exact test, Pearson's chi-square test, and intraclass correlation coefficient (ICC). P<0.05 was considered statistically significant.

A total of 96 patients were enrolled, including 10 who achieved pathological complete response (pCR). Suspicious microcalcifications were associated with benign pathology in 10.4% (10/96) of patients. Among the remaining 86 patients without pCR, residual microcalcifications were associated with invasive or in-situ carcinoma in 61.5% (59/96) and with benign pathology in 28.1% (27/96). The proportion of residual malignant microcalcifications was highest in hormone receptor-positive (HR+) patients compared with HR-negative (HR-) patients (48.9% vs. 13.5%, respectively; P=0.019). MRI was superior to residual microcalcifications on mammography in predicting residual tumor extent across all subtypes (ICC=0.709 vs. 0.365). MRI showed higher correlation with residual tumor size for HR/HER2+ and HR/HER2- subtypes (ICC=0.925 and 0.876, respectively).

After NAC, the extent of microcalcifications on mammography does not correlate with the extent of residual cancer in 38.5% of women. Regardless of the extent of microcalcifications, microcalcifications, residual tumor extent on post-chemotherapy MRI, and molecular subtype may serve as accurate tools for evaluating post-chemotherapy residual cancer.