The subtype of breast cancer is an important factor affecting subsequent mortality. Non―luminal breast cancer has been considered to have high―grade malignancy. The purpose of this study was to clarify the subtype of breast cancer detected by ultrasound(US)and mammography(MG)screening. Screening using US and MG was performed for 28,691 and 40,282 women, respectively, between January 2009 and December 2011 at our preventive medicine center. Cancers were detected in 112(0.39%, 124 lesions)and 97(0.24%, 101 lesions)women by US and MG, respectively. We investigated the subtypes of 74 US―detected invasive cancers and 59 MG―detected invasive cancers, and the following results were obtained: US: Luminal A(LA)25 (33.8%), Luminal B(LB)38(51.4%), LA/B6(8.1%), HER22(2.7%), and triple negative (TN)3(4.1%). MG: LA13(22.0%), LB32(54.2%), LA/B3(5.1%), HER26(10.2%), TN4(6.8%), and HER2/TN1(1.7%). In our series luminal cancers were detected more often overall by US than by MG(p<0.001). Thirty―seven cancers were detected among 11938 subjects, who underwent both MG and US. Only three non―luminal cancers were detected; all of them were detected by MG and none was detected by US alone. Although US is effective for detecting MG―negative breast cancer in dense breasts, our results suggest that additional US is of limited utility for detecting non―luminal cancer with a high grade of malignancy.
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