To investigate the application of the ultrasound diffusion breast imaging(UDBI) system in the diagnosis of T₁ stage breast cancer.

Totally 2 245 patients with ultrasound grade 3 and above (the patients in grade 6 were excluded) in the Chengdu Women’s and Children’s Central Hospital from April 2016 to April 2018 were included in this study. The patients underwent both ultrasonography and UDBI. Among them, 1 157 patients underwent biopsy, with complete pathological data, so they were retrospectively analyzed. According to the maximum diameter of the tumor, 1 157 cases were divided into 3 groups: 452 cases in S1 group (≤1.0 cm), 489 cases in S2 group (1.1-2.0 cm), and 216 cases in S3 group (>2.0 cm). The receiver operating characteristic (ROC) curve was used to analyze the diagnostic performance of the two methods. The area under the ROC curve and 95%CI were calculated accordingly. The area under the ROC curve was compared by Z test using the Medcalc V19.0.4 software. The sensitivity and specificity of the two methods were compared by χ² test or Fisher exact test. The paired χ² test (McNemar test) was used to compare the two methods with pathological results.

Among the 1 157 cases, there were 144 cases of malignant tumor (12.4%), confirmed as invasive ductal carcinoma, 1 013 cases of benign disease (87.6%), including 852 cases of fibroadenoma, 49 intraductal papilloma and 112 adenosis. The sensitivity, specificity and diagnostic accuracy in the diagnosis of breast cancer were 90.2% (130/144), 67.7% (686/1 013) and 70.5 (816/1 157) by ultrasound, 94.4% (136/144), 81.8% (829/1 013) and 83.4% (965/1 157) by UDBI, respectively. The diagnostic accuracy and specificity of UDBI were significantly higher than those of ultrasound (χ²=55.148, P<0.001, χ²=53.515, P<0.001), while the sensitivity of the two methods showed no significant difference(χ²=1.772, P=0.183). The ROC curve showed that for the tumor with the diameter of 0-1.0 cm or 1.1-2.0 cm, the diagnostic performance of UDBI was superior to that of the ultrasound (Z=2.384, P=0.034; Z=3.962, P<0.001); for the tumor with the diameter >2.0 cm, there was no significant difference in the diagnostic performance between UDBI and ultrasound (Z=1.911, P=0.056). Subgroup analysis showed that for the tumor with the diameter of 0-1.0 cm, the specificity of UDBI was significantly higher than that of ultrasound [85.7% (359/419) vs 72.3% (303/419), χ²=22.555, P<0.001]. For the tumor with the diameter of 1.1-2.0 cm, the specificity of UDBI was significantly higher than that of ultrasound [80.4% (349/434) vs 66.1% (287/434), χ²=22.613, P<0.001]. For the tumor with the diameter >2.0 cm, the specificity of UDBI was significantly higher than that of ultrasound [73.1% (117/160) vs 58.1% (93/160), χ²=7.979, P=0.005]. There was no significant difference in the sensitivity between UDBI and ultrasound in each subgroup (P=0.427; χ²=0.374, P=0.541; P=1.000).

The UDBI is superior to ultrasound in the diagnosis of breast cancer of T₁ stage, which can be used as an effective method for early breast cancer diagnosis.