Background: Each year thousands of women present,to general surgeons with palpable breast masses, some of which are clinically ambiguous and the majority of which are benign. In addition, surgeons are frequently faced with the question of whether to biopsy those palpable abnormalities in the setting of normal radiographic studies. One might propose that such lesions could be safely observed rather than immediately biopsied. If these lesions were not biopsied, how many cancers would escape detection? To address this issue, a population of patients with known, palpable breast cancer was retrospectively examined to determine the frequency of normal or benign findings on both mammography and ultrasonography. Methods: Between January 1998 and December 2001, 351 women with breast carcinoma presented initially with palpable tumors. The medical records of these remaining 351 cases were retrospectively reviewed to examine the radiographic characteristics of the palpable carcinomas. Results: Of the 351 cases in the study group, 13 (3.7%) patients with palpable breast cancers had mammogram, and sonogram examinations that were both normal, benign, or nonspecific in appearance. Conclusions: The results of this study indicate that nearly 4% of women with breast cancer who present with palpable lumps will have normal or benign findings on both mammography and ultrasonography. These data support prior studies of similar false negative rates and may provide some reassurance to surgeons and patients regarding clinical breast lumps, as the decision of whether to biopsy still rests in the surgeon's hands. However, inappropriate reliance on these tests for an evaluation of a palpable abnormality will result in a number of missed tumors. (C) 2003 Excerpta Medica, Inc. All rights reserved.