Cytohistologic features of invasive micropapillary carcinoma in a young female.

Invasive micropapillary carcinoma (IMPC) is a recently reported variant of breast carcinoma in women. There has been only a single report describing the cytologic features of IMPC in the literature. We report on the cytohistologic features of IMPC with diffuse involvement of two quadrants of the breast and axillary lymph node metastases in a 32-yr-old female. The cytologic appearance of IMPC was characterized by high cellularity, marked cell discohesion, and epithelial cells forming aggregates, morules, and angular and papillary clusters without fibrovascular cores and showing high nuclear/cytoplasmic ratio, irregular nuclear contours, and finely stippled chromatin. Occasional psammoma bodies were noted. Histologic examination showed a pure IMPC composed of clusters, morules, and aggregates of malignant epithelial cells surrounded by distinctly clear spaces separated by thin fibrovascular septa. The tumor involved both inner quadrants and axillary lymph nodes. A primary tumor elsewhere, particularly in the ovaries, was excluded. The patient has been disease-free 38 mo after the initial diagnosis.