RESUMO
<p><b>BACKGROUND</b>Although cytological methods for breast oncology have been used in recent decades, intra-operative frozen section has been playing a vital role in making therapeutic decisions. We analyzed a large series of frozen section diagnoses for Chinese cases of breast lesion within the last 15 years. The experience was expected to increase the diagnostic accuracy of cases with breast lesions.</p><p><b>METHODS</b>The data from consecutive 13243 cases of breast lesions diagnosed with intra-operative frozen sections between 1988 to 2002 were compared with paraffin sections in a case by case manner. The causes of false negative and positive diagnoses as well as delayed diagnoses were analyzed.</p><p><b>RESULTS</b>One hundred and seventeen cases (0.9%) were falsely diagnosed, with one false positive case and 116 false negative cases. The diagnosis of 47 cases (0.4%) was delayed. The proportion of several lesions had the features of the patients' ages. Six types (false invasion, peri-papilloma, adenoma of nipple duct, florid adenosis, sclerosing adenosis, and granulose cell tumor) of lesions may lead to false positive, and four types (morphological changes responding chemotherapy, well differentiated papillary carcinoma, invasive lobular carcinoma, and tubular carcinoma) to a false negative. Gross and microscopic findings may be inconsistent in two types of lesions (radial scar and florid adenosis) microscopic and clinical findings in three types (ganulomatous mastitis mammary, duct ectasia, and fat necrosis), and three types (abundant fat or sclerous tissues; borderline lesions and changes of post-chemotherapy) were likely wrongly classified.</p><p><b>CONCLUSIONS</b>Intra-operative frozen section can accurately identify breast lesions in many instances, leading to fewer errors on account of more diagnostic experience and understanding of diagnostic limitations.</p>