Objective: To explore the ultrasonographic and pathological features for different types of mucinous breast carcinoma(MBC), and to analyze the causes for ultrasonic misdiagnosis. Methods: A total of 68 MBC patients with 70 lesions were enrolled, and ultrasonographic manifestations, clinical data and pathological results were analyzed retrospectively. Results: Among 68 patients aging from 30-86 years old (54.5±23.3 years old), 40 cases (58.8%) were over 50 years old.Pathology examination revealed that pure MBC accounted for 57.4% (39/68), and the other cases were mixed MBC(42.6%,29/68); 16.2% of patients(11/68) had lymph node metastasis. Among the 70 lesions, 41.4%(29/70) were located on the right breast, 58.6% (41/70) on the left breast. In addition, the locations of 41.4%(29/70) lesions were outside the upper quadrant. Irregular morphology was observed in 76.9% (30/39) of pure MBC lesions, and in 80.6% (25/31) of mixed MBC lesions.Lobulated pure MBCs were more than mixed MBCs(25 cases to 7 cases)（P<0.05). There was 48.7% (19/39) of pure MBC lesions with unclear boundary, while there was 77.4%(24/31) of mixed MBC lesions with it. Both pure MBC and mixed MBC lesions showed more posterior acoustic enhancement on ultrasonography [74.4%(29/39) and 48.4% (15/31), respectively]. Blood flow were detected in 71.8% cases (28/39) of pure MBC and in 80.6% cases(25/31) of mixed MBC.The pure MBC and mixed MBC lesions that were classified as suspicious or malignant by BI-RADS accounted for 87.2% (34/39) and 93.5% (29/31) respectively, and the misdiagnosis rates were 12.8% (5/39) and 6.5% (2/31). The misdiagnosed masses were characterized by regular morphology, the clear boundaries and the absence of posterior acoustic enhancement,which accounted for misdiagnosis. Conclusions: The ultrasonic manifestations of MBC have certain relationship with pathological type of MBC. The lesions of pure MBC are usually lobulated with unclear boundary and enhancement of posterior acoustic features, which make it difficult to distinguish between benign and malignant lesions. Mixed MBC presents with more aggressive imaging characteristics on the ultrasonography.