In an attempt to reduce the number of breast biopsies done for benign breast disease in patients with breast lumps, we evaluated prospectively the sensitivity and specificity of the combination of three diagnostic modalities: clinical examination, mammography, and fine-needle aspiration cytologic examination (FNA). A total of 234 patients with a breast mass had a physical examination, a mammogram, and FNA, and were listed as malignant/suspicious or benign. All patients underwent a subsequent biopsy: 110 were found to have breast cancer, and 124 had a benign lesion. The sensitivity and specificity of the individual tests were as follows: 89% and 73%, respectively, for mammographic examination; 93% and 97% for FNA cytologic examination; and 89% and 60% for physical examination. For the combined triad of tests, the sensitivity was 100% and specificity 57%. All patients who had breast cancer had positive findings for malignancy in one or more of the diagnostic tests, i.e., 100% sensitively. All patients who had negative findings for malignancy in all three diagnostic tests had benign lesions, i.e., a negative predictive value of 100%. We conclude that breast masses can be diagnosed with a high degree of accuracy by combined physical, mammographic, and fine-needle aspiration cytologic examination. Patients in whom physical examination, mammography, and FNA were negative for malignancy can be safely observed, obviating the need for an open biopsy.

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Ras mutations are an important early event in a number of carcinogen-induced rodent tumors. Colon carcinogenesis induced in rats by azoxymethane is a useful model as it mimics the adenoma-carcinoma sequence observed in humans. In addition, aberrant crypt foci develop in the rat and these lesions appear to be potentially important precursors to adenomas in colorectal cancer. Recent studies have shown that specific K-ras codon 12 and 13 mutations are present in up to 66% of carcinogen-induced rat colon adenocarcinomas. We studied the frequency of these mutations during the aberrant crypt focus-adenoma-carcinoma sequence in azoxymethane-induced Fisher F344 rats. K-ras codon 12 GAT and codon 13 GAC mutations were detected with a sensitive assay based on the amplification of DNA using the polymerase chain reaction. No mutations were present in normal mucosa. Of 27 aberrant crypt foci, K-ras mutations were identified in 2 lesions containing 5 and 10 aberrant crypts, respectively. Mutations were present in 1 of 23 and 10 of 27 adenomas and adenocarcinomas, respectively. These data suggest that K-ras mutations play a role during the stages of carcinogenesis in azoxymethane-induced rat colon cancer. The demonstration of a genetic mutation in aberrant crypt foci provides further evidence for the significance of these lesions as precursor markers of malignant potential during colorectal tumorigenesis.