The cytopathology of metastatic breast cancer.

A comparison was made between the histopathologic and cytopathologic appearances of 45 cases of metastatic breast cancer and the histopathologic appearance of their primary neoplasms. Metastatic infiltrating duct carcinoma in body cavity fluids presented with an admixture of single cells and tissue fragments in a ratio of 0.86 to 1. The most commonly occurring tissue fragments were well circumscribed round to oval masses of cells, true acini and cells in tandem arrangement. The cells of metastatic infiltrating duct carcinoma were very pleomorphic ranging from 11.5 to 22 micrometers in diameter. Metastatic infiltrating lobular carcinoma in body cavity fluids presented as a population of primarily single cells with a ratio of 13 single cells to each tissue fragment. The rare tissue fragment encountered was a group loosely cohesive cells without nuclear molding by the cytoplasm of adjacent cells. The individual cells had extremely high nuclear/cellular ratios and were uniform in size ranging in diameter from 10.5 to 14 micrometers. The presentation of metastatic infiltrating lobular carcinoma was very similar to that of lymphomas in body cavity fluids and cerebrospinal fluids and may pose a problem in differential diagnosis.