Another example of mucinous carcinoma of breast. The tumor has ill-defined margins as compared to the previous case. This is seen more often in tumors with mixed mucinous and ductal differentiation.
About the Disease
Pure mucinous (colloid) carcinoma makes up about 2% of all breast carcinomas. Focal mucin production is seen in additional 2% of breast cancers. The term mucinous carcinoma is restricted to the tumors showing stromal mucin in >90% of the tumor and excludes 1) mixed tumors containing areas of ordinary invasive ductal carcinoma, and 2) signet ring-cell carcinomas. The patients are usually post-menopausal. The tumors are well-circumscribed and have a gelatinous, bluish-gray cut surface. Microscopically, well-differentiated tumor cells arranged in solid nests, trabecular formations, cribriform clusters, or papillary structures are seen floating in pools of copious extracellular mucin.Immunohistochemical profile: Mucinous carcinoma shows strong cytoplasmic positivity for MUC2 and decreased MUC1 immunoreactivity when compared to ductal carcinoma. Hormone receptors ER and PR are always positive; HER2 is negative. Many cases express WT1. Between 25% to 50% of cases show neuroendocrine differentiation and are positive for NSE and related markers. Mucinous carcinomas types A and B. Some authors have proposed subclassification into types A and B. Type A mucinous carcinomas are a distinct entity. Type B tumors show neuroendocrine differentiation. The short-term prognosis of mucinous carcinoma of breast is excellent. However, the tendency for delayed recurrences necessitates long-term follow-up. The incidence of nodal metastases is 2-4%. The presence of neuroendocrine differentiation does not appear to affect the prognosis.