Invasive micropapillary carcinoma. Distinct features of a poorly recognized variant of breast carcinoma.

Abstract

Invasive micropapillary carcinoma (IMC) is a histological variant of breast cancer with a poor prognosis. Pathological findings of 15 cases of IMC are compared with those of 144 invasive duct carcinoma (IDC) and 10 invasive papillary carcinoma (IPC). Only 33% of cases were diagnosed in stage I. Mean tumor size was 2.3 cm. Nuclear grade 3 was found in 60% of cases, aneuploidy in 78%, and 92% had hormone receptors. Nine patients showed lymph node metastasis. Tumor size, nuclear grade, mitotic rate and lymph node involvement were higher in IMC when compared with IDC grade I and IPC, but not when compared with IDC grade II and III. Four cases of IMC (27%) recurred before two years. Recurrences and lymph node metastases showed the same architectural pattern as the primary tumor. IMC shows a high incidence of lymph node involvement and a high early recurrence rate.