Interpretation of fine needle aspiration cytology of the breast: a comparison of cytological, frozen section, and final histological diagnoses

This study examines the performance of the preliminary, on-site interpretation by the pathologist of fine needle aspiration (FNA) cytology smears compared to the final cytology report, the frozen section diagnosis and the final histopathological report. We found that both the preliminary and the final cytology reports gave satisfactory results over the minimum standards for quality assurance required by both the Norwegian breast screening programme and the NHS BSP in the UK with the exception of the 'suspicious' rate. We noted that the preliminary report had fewer false negatives (2.1%) than the final report (4.3%). We show that an unequivocal cytological diagnosis of malignancy is a reliable diagnosis, and in cases where mammography/ultrasonography and clinical examination are in agreement with FNA, frozen section examination is unnecessary. However, cases with a suspicious or equivocal FNA should be considered for frozen section analysis.