Primary Signet Ring Cell Carcinoma Bilateral Breast: An Exceptional Occurrence.

Signet ring cell carcinoma (SRCC) of the breast is an exceptionally rare subtype accounting for only 0.04% to 2.7% of all breast cancers. Pure SRCC is characterized by the presence of >90% signet ring cells and exhibits an aggressive clinical profile often associated with higher histologic grade, lympho-vascular invasion, hormone receptor positivity, and low HER2 expression. Differentiating primary mammary SRCC from metastases from gastrointestinal primary, especially in elderly patients with bilateral presentations is of prime importance. Immunohistochemistry plays a crucial role in this regard with primary breast SRCCs displaying ER, GATA3 and CK7 positivity and CK20 and CDX2 negativity. We report a case of bilateral signet ring cell carcinoma breast in an 82 year-old female. This case highlights the significance of recognising SRCC breast as a distinct pathological entity and thorough evaluation in case of bilateral presentation as it is exceptionally uncommon and poses diagnostic and therapeutic challenges.