Abstract
Background : Triple-negative (TN) breast cancer is immunohistochemically characterized as estrogen receptor-, progesterone receptor-, and HER2-negative. We conducted a detailed analysis of the cytologic characteristics of TN and basal-like (BL) breast cancer in an attempt to enable cytologic diagnosis of TN and BL breast cancer.
Study Design : A total of 54 cases of TN breast cancer were included in this study. Of these, 41 cases that were positive for either or both cytokeratin 5/6 and EGFR were regarded as BL breast cancer. A total of 20 cases of the luminal subtype and 10 cases of HER2-positive cancer were included. Specimens of these groups were extensively reviewed with respect to 13 morphologic factors.
Results : The tumor cells of TN/BL breast cancer appeared as scattered clusters, without gland formation, often associated with lymphocytes in a necrotic background. They had larger and naked nuclei, giant cells, and squamous metaplasia-like changes were also observed.
Conclusions : The cytologic findings of the TN and BL groups were almost similar. The differences in the cytologic findings between the TN/BL group and the HER2 group were minor, and meticulous observation was required to differentiate between the two. However, the above-mentioned cytologic characteristics of TN/BL breast cancer were useful for discriminating it from luminal-type breast cancer, which is the most frequently encountered type of invasive ductal carcinoma.
