Invasive lobular carcinoma of the breast with extracellular mucin- a new rare variant.

Historically, extracellular mucin secretion is by default a feature of ductal carcinoma. Lobular carcinoma is known to be associated with only intracytoplasmic mucin production and signet ring cells. As ductal carcinoma and lobular carcinoma have different therapeutic and prognostic implications, it is important to classify them into respective groups. Here, we present a case of invasive lobular carcinoma with abundant extracellular and intracellular mucin in a 38-year-old female patient. Invasive lobular carcinoma with extracellular mucin is an extremely rare and new variant. Only 3 cases are reported in the literature so far.