Diagnostic dilemma in cytologic features of micropapillary carcinoma of the breast: A report of 2 cases

Abstract

Background: Invasive micropapillary carcinoma (IMPC) is a rare type of breast carcinoma with unique morphologic 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. Cases: We reviewed the cytologic features of 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. Conclusion: 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. © The International Academy of Cytology.