Fine needle aspiration cytology of invasive micropapillary carcinoma of the breast

Abstract

To determine the pathognomonic diagnostic cytological features of invasive micropapillary carcinoma of the breast which is a poor prognostic subtype of infiltrating ductal carcinoma. A series of 20 histologically proven tumours were reviewed retrospectively to evaluate the various cytological features, including tumour morules, isolated malignant cells, staghorn epithelial structures, mucinous background and apocrine metaplasia. Tumour morules formation and isolated malignant cells were the two most reliable and constant cytological features, being present in 75% (15/20 cases) of cases. Staghorn epithelial structures were present in 35% (7 cases). Mucinous background (2 cases, 10%) and apocrine metaplasia (4 cases, 20%) of the tumour cells were seen in a few cases only and did not appear very helpful. Tumour morules formation, isolated malignant cells and staghorn epithelial structures are the most reliable cytological features, and the presence of these should raise suspicion of invasive micropapillary carcinoma.