False-positive reports in fine needle biopsy of breast lesions

A review of the literature reveals considerable variations in the diagnostic accuracy of fine needle biopsy (FNB) of breast lesions between series, partly due to different methods of calculation, different definitions, and insufficient numbers of cases with adequate follow-up to provide reliable statistics. The best larger series have a false-positive rate between 0.2 and 0.3%, slightly higher for non-palpable than for palpable lesions. The cytological patterns of a range of benign lesions which may cause diagnostic difficulties and may be misdiagnosed as malignant by FNB are described, and guidelines to reduce the risk of false-positive diagnoses are proposed.