Primary signet ring cell carcinoma of the breast: A rare entity with unique biological behavior-A clinical study based on pure signet ring cell carcinoma cohort

Background: Primary signet ring cell carcinoma (SRCC) of the breast is a rare entity, and only a few case reports of the pure SRCC cases could be found in English literatures. We summarized the clinicopathological characteristics of a relatively large cohort of pure breast SRCCs for the first time. Methods: We reviewed the medical records of 23 cases of pure breast SRCC with a median follow-up time of 70 months. Results: Three patients had bilateral primary breast cancer (BC) and two of them had bilateral pure SRCCs. 30 % of patients had the malignant tumor family history including two bilateral BC patients. Malignant calcification was observed in 35.3 % of mammography images. Multifocal lesions were microscopically found in 26.1 % of cases. 63.6 % of the cases had lymph node metastasis, 45.5 % were classified as Stage III, 69.6 % had high value of Ki-67 index, and 34.8 % were triple negative subtype. 19.0 % of patients had local recurrence, and 52.6 % had distant metastasis. Four in five patients with positive tumor family history and follow-up data had relapse of SRCC. The 5-year overall survival rate was 73.7 %, the 5-year relapse-free survival rate was 54.3 %, and the 5-year breast cancer specific survival rate was 78.3 %. Conclusion: Pure SRCC of the breast showed an aggressive behavior. Neoadjuvant chemotherapy could be considered, breast-conserving surgery should be prudently chosen, and axillary lymph node dissection may be necessary. The high rate of positive tumor family histories and high bilateral incidence, which showed an adverse effect on prognosis, indicate the unique genetic burden of SRCC.