Abstract Background: In diagnosis of non-palpable calcificated breast cancer (NPCBC), stereo-guided mammotome (ST-MMT) serves as the standard. However, ultrasound resolution has improved dramatically recently. We hypothesized that through ultrasonography, it will become possible to diagnose NPCBC by US guided examination such as fine needle aspiration cytology (FNAC) and core needle biopsy (CNB) with much less invasion than ST-MMT. Method: (Study1) The results of ultrasonic detection ability and US guided examination were studied among the benign lesions of 35 cases and 90 NPCBC patients histologically diagnosed in our facilities from 2010 to 2012. Of the 90 histological types, 74 (82%) were DCIS, and 16 (18%) were invasive carcinoma. (Study 2) The results of 193 progress observation cases from 2008 to 2012 with Birads Category 3 and 4a calcification were examined. Result: (Study1) Using ultrasonography (Toshiba Aprio XG), calcification was detected in 88 of the 90 NPCBC lesions as echogenic foci. Two non-detectable lesions were DCIS of Van Nuys 1 and Van Nuys 2. The results of the FNAC were 80% positive and 20% indeterminate (there were no negative cases). In the 88 cases of possible calcified substance extracted through FNAC, 99% were confirmed under microscopic observation. (Study 2) 163 of 193 cases were able to be followed-up every six months for two to four years. An increase in calcification was observed in nine cases. Five of these cases were diagnosed with DCIS: Four were Van Nuys 1; one was Van Nuys 2. All five cases were of low-grade-malignancy. Conclusion: The diagnostic method using FNAC to visualize calcification using high-resolution ultrasonography is an effective method to reduce the non-efficient, invasive breast cancer detecting method of ST-MMT. The diagnostic method is particularly useful in women of small breast size in Asian countries. The few low-grade DCIS cases included were not detected with ultrasound. However, we believe it is not a diagnostic error. As a result, we stopped using the ST-MMT from 2010. In spite of this, in the MMG screening performed in our facilities from 2010 to 2012, the detection rate of NPCBC without mass on MMG was 0.17 %. This detection rate is excellent in our country. Citation Format: Arai T, Takebe K. Contribution of high-resolution ultrasonography in the diagnosis of non-palpable breast cancer with calcification. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P4-03-07.