Diagnosis and subclassification of breast carcinoma by fine-needle aspiration biopsy - Results of the interlaboratory comparison program in non-gynecologic cytopathology

Context.-The College of American Pathologists Interlaboratory Comparison Program in Non-Gynecologic Cytopathology is a popular educational program for nongynecologic cytology that had 1018 participating laboratories by the end of 2000. Data generated from this program allow for tracking performance on slides in a diverse group of laboratories. Objective.-We reviewed the performance of participating laboratories on fine-needle aspiration biopsies of the breast with particular interest in the ability of participants to accurately subclassify breast carcinoma. Design.-We reviewed the responses of participating laboratories for glass slides of breast fine-needle aspiration biopsies for the year 2000. We analyzed benchmarking data provided for each specific diagnosis. Results.-The overall false-negative rate for laboratories was 6.2%, and the overall false-positive rate was 1.1%. Most of the breast carcinomas were correctly identified as malignant on the general diagnosis, but participants had more difficulty subclassifying types of breast carcinoma. The rate of correct exact diagnosis was 65% for ductal adenocarcinoma, 20% for lobular adenocarcinoma, 12% for medullary carcinoma, and 27% for mucinous carcinoma. Conclusions.-This study shows that fine-needle aspiration biopsy of the breast is a reliable method for the diagnosis of breast carcinoma, but difficulties still exist in our ability to determine tumor subtype.