Atypia in fine needle aspirates of breast lesions

The atypical category is controversial in fine needle aspiration cytology (FNAC) of the breast; most are benign, but a significant number are malignant. To date, no morphological criterion has been found to be consistent in predicting malignancy.

To evaluate specific cytological parameters and assess their usefulness in predicting histological outcome in a cohort of atypical breast FNAC, in order to establish a set of objective criteria in defining 'high risk' atypical breast FNAC.

A retrospective review of 98 cases of atypical breast FNAC with histological correlation was undertaken. The cytological preparations were evaluated for cellularity, percentage of epithelial cell cluster and single epithelial cells, nuclear atypia, nucleus:cytoplasm ratio, percentage of bipolar nuclei, and the presence of stromal fragments, histiocytes and necrosis.

66 of 98 cases (67.35%) showed benign histology and 32 cases (32.65%) showed malignant histology. Compared with the malignant group, the benign group had significantly lower patient age (p=0.05), higher bipolar nuclei (p<0.0001), less degree of nuclear pleomorphism (p<0.0001), lower nucleus:cytoplasm ratio (p<0.0001), lower cellularity (p=0.05) and less necrosis (p<0.001). There was no difference in the percentage of epithelial clusters and single cells, or the presence of stromal fragments and histiocytes.

The presence of nuclear pleomorphism, high nucleus:cytoplasm ratio, epithelial cell atypia, low number of bipolar nuclei and necrosis are useful parameters to predict malignancy in atypical FNAC of the breast. Assessment of these factors in atypical FNAC may be helpful in predicting cancer risk and subsequent management decision making.