Breast carcinoma with spontaneous regression after needle biopsy: a case report and literature review.

Background: Spontaneous regression (SR) of cancer is a rare condition in which the cancer partially or completely disappears without treatment. We report a case of breast cancer with tumor regression and spontaneously induced T-cell-mediated immunological responses in a surgical specimen obtained after core needle biopsy (CNB). Case Description: A 52-year-old woman presented with a mass in the right breast. Mammography showed a high-density mass with fine serrated margins in the right lower outer quadrant. Breast ultrasonography showed an irregular hypoechoic mass with a maximum diameter of 22 mm. CNB was performed and revealed an invasive ductal carcinoma with negative estrogen receptors, positive progesterone receptors, and negative HER2 (1+). The Ki67 index was 70% to 80%. Luminal B cT2N1M0 stage IIB right breast cancer was diagnosed. Although preoperative chemotherapy was considered, surgery was selected because of her history of schizophrenia. She underwent right mastectomy and axillary lymph node dissection. A postoperative pathological analysis revealed a 20 mm × 10 mm × 10 mm mass. However, most areas of the mass regressed and appeared as necrotic tissue with no obvious invasive areas. Only intraductal extension was observed in one glandular duct. Axillary lymph node metastases were not observed. These results suggest that the tumor may have spontaneously regressed, possibly because of the CNB procedure. Follow-up without treatment was performed, and no recurrence occurred during 2 years after surgery. Conclusions: Invasive ductal carcinoma may spontaneously regress after preoperative CNB.