Fine-needle aspiration cytology of breast lesions: a review of cytological analysis using smooth muscle actin (SMA) immunostaining.

We reviewed fine-needle aspiration (FNA) cytology cases for breast lesions in order to improve the reliability of cytological diagnoses. We analyzed the results of 1,019 FNA cytology cases of patients with breast lesions for five years in our hospital. One hundred and ninety-seven (19.3%) of the 1,019 cases were examined using histological sections, in addition to cytological specimens, and included 27 cytologically suspicious cases. Of the 1,019 cytology cases, 606 (59.5%) were benign, 41 (4.0%) suspicious, 149 (14.6%) malignant and 223 (21.9%) inadequate/nondiagnostic. We also performed immunostaining against smooth muscle actin (SMA), using 19 cytological specimens and 88 histological specimens. We observed myoepithelial cells positive for SMA, which were valuable for cytological or histological diagnosis. To improve the reliability of cytological diagnoses and decrease the false-positive and false-negative cases, it is very important to obtain sufficient aspirates and to understand the cytological characteristics of various benign and malignant breast lesions.