BACKGROUND The association between method of detection and breast carcinoma histopathology has not been assessed adequately in a population-based setting. METHODS Among women who were included in a population-based, case-control study of breast cancer, patients who were newly diagnosed with invasive breast carcinoma were identified from Wisconsin's statewide tumor registry. Only women age > or = 50 years were analyzed, because screening by mammography was not recommended before age 50 years at the time of the study. The breast tumors among these women (n = 2341 tumors) included the following histopathologies: lobular carcinoma (n = 206 tumors); ductal carcinoma, not otherwise specified (n = 1920 tumors); papillary carcinoma (n = 15 tumors); medullary carcinoma (n = 36 tumors); mucinous adenocarcinoma (n = 56 tumors); tubular adenocarcinoma (n = 41 tumors); invasive comedocarcinoma (n = 24 tumors); scirrhous adenocarcinoma (n = 15 tumors); and mixed ductal/lobular carcinoma (n = 28 tumors). RESULTS Overall, women reported that 41% of tumors were detected by mammography, 48% of tumors were self detected, and 11% of tumors were detected by clinical breast examination (CBE). Detection by mammography was significantly more likely for women who had tubular carcinoma (83%; P < 0.001) and invasive comedocarcinoma (67%; P = 0.23) compared with women who had ductal carcinoma (40%). Mammography was significantly less likely to detect medullary carcinoma (17%) than ductal carcinoma (40%; P = 0.01). Lobular carcinoma was the only histopathology that, compared with ductal carcinoma, was detected significantly more often by CBE than by self detection. Mammography detected lobular carcinoma (42%) as frequently as ductal carcinoma (40%). However, the use of postmenopausal hormones may have modified these detection patterns: Among current users, mammography discovered a greater percentage of ductal carcinomas (51%) and fewer lobular carcinomas (36%) than nonusers. CONCLUSIONS Among women age > or = 50 years, breast cancer detection by mammography, self detection, and CBE varied according to tumor histopathology.