Invasive micropapillary carcinoma of the breast: eighty cases of an underrecognized entity

Eighty cases of infiltrating duct carcinoma of the breast with a pure or partial micropapillary component are reported. The cases were analyzed using various parameters, including age at presentation, tumor size, tumor grade, presence of lymphatic invasion, and axillary lymph node status. The patients' age at presentation ranged from 36 to 92 years (mean, 58.8 years). Tumor size ranged from 0.1 to 10 cm (mean, 2.0 cm); 67.5% (54 of 80) were poorly differentiated, and 32.5% (26 of 80) were moderately differentiated; 62.5% (50 of 80) of the cases had lymphatic invasion; 72.3% (47 of 65) of cases with axillary dissections had positive lymph nodes; and 25% (20 of 80) of the tumors were < or = 1.0 cm and 7.5% (6 of 80) were < or = 0.5 cm. The characteristics of these small tumors with an invasive micropapillary component have not previously been reported. Despite their minute size, these small micropapillary carcinomas seem to show the same proclivity for lymphatic spread and nodal dissemination as larger tumors with this unique histologic pattern.