Diagnostic accuracy of fine-needle aspiration cytology of the breast in Japan: report from the Working Group on the Accuracy of Breast Fine-Needle Aspiration Cytology of the Japanese Society of Clinical Cytology.

The Working Group of the Japanese Society of Clinical Cytology was assembled to assess the current status of breast cytology in Japan by conducting a large-scale survey regarding the accuracy of fine-needle aspiration biopsy (FNAB) in Japan. We collected data and investigated the status of breast cytological diagnosis at 12 different cooperating facilities in Japan, and re-evaluated their false-negative and false-positive cases. Among 30,535 individuals who underwent a breast cytological examination, analyses were conducted on 10,890 individuals (35.7%) in whom cytological diagnoses were confirmed by histology. Among these patients, the cytological diagnosis had an inadequate rate of 17.7%, an indeterminate rate of 7.8%, a positive predictive value of 'malignancy suspected' cells of 92.4%, an absolute sensitivity of 76.7%, a complete sensitivity of 96.7%, a specificity of 84.3%, a positive predictive value of 'malignant' cells of 99.5%, a false-negative value of 3.31%, a false-positive value of 0.25% and an accuracy rate of 88.0%. Subsequently, 297 false-negative and 23 false-positive cases were re-evaluated and several factors were characterized (i.e. histological type, tumor size and misread points). This survey collected data from a large number of cases for breast FNAB. Based on our survey, the accuracy of FNAB in Japan was relatively high compared with the goal of assessment of diagnostic accuracy. However, there were some false-negative and false-positive cases. Improvements in accuracy resulting from the learning points in the present study will lead to more useful and reliable diagnostic tools in clinical practice.