ABSTRACT
BACKGROUND: Invasive lobular carcinoma is the second most common histological type of breast carcinoma, accounting for approximately 5%-15% of all invasive breast cancers. The extracellular mucin secretion is by default a feature of ductal carcinoma. Only four cases of infiltrative lobular carcinoma with extracellular mucin have been report. CASE SUMMARY: A 60 year old female asymptomatic patient with palpable breast mass and architectural distortion by mammography on external upper quadrant of the right breast was diagnosed as invasive lobular carcinoma with extracellular mucin in the resection, confirmed with immunohistochemistry markers. DISCUSSION: Previous report in the literature of four cases of Invasive lobular carcinoma of breast with extracellular mucin, all of them sharing the same histologic features: the presence of extracellular and intracellular mucin with appearance of infiltrates lobular carcinoma with signet ring cells and "Indian files". CONCLUSION: It is important to know that extracellular mucin production is not exclusive of ductal lesions and keep in mind the lobular carcinomas with extracellular mucin as a differential diagnosis.
