Diagnostic Dilemma in Cytologic Features of Micropapillary Carcinoma of the Breast

Abstract
Invasive micropapillary carcinoma (IMPC) is a rare type of breast carcinoma with unique mophologic features and high frequency of axillary lymph node metastasis. Recognizing the IMPC on cytology makes it possible to identify a group of patients with a poor prognosis and may alter the adjuvant treatment. We reviewed the cytologic features of a 2 IMPC cases 50-year-old women. Both cases included conventional findings of IMPC, such as increased cellularity, cell clusters with angular and papillary configuration without a fibrovascular core, tumor clusters showing an "inside-out" pattern and the presence of single discohesive cells. Of interest, both cases included a few malignant-appearing multinucleated giant cells. The slides of 1 case were included a little mucin in the background of tumor diathesis. There were no psammoma bodies in the smears. The cytologic features of IMPC are unique and should be recognized because of its' tendency to infiltrate the axillary lymph nodes. In addition to well-known cytologic features of IMPC, multinucleated giant cells and a scanty amount of mucin should also alert the cytopathologist to the possibility of IMPC.