To investigate the typical and atypical ultrasound features of breast fibroadenoma, and analyze the causes of ultrasound misdiagnosis.

A retrospective analysis was performed on 392 cases (401 masses) of breast fibroadenoma confirmed by surgery and pathology at Taihe Hospital Affiliated to Hubei Medical College from 2015 to 2020. Based on the pathological results, we compared the ultrasonic misdiagnosis rate by patient ages, tumor diameter, atypical feature, and pathological type.

Among the 401 masses included, 123 atypical features were observed by ultrasonography, of which 40 were correctly diagnosed and 83 were misdiagnosed; 278 cases with typical ultrasonic features were diagnosed correctly. The misdiagnosis rate of lesions with a diameter less than 1 cm (31.5%) and larger than 3 cm (34.9%) was significantly higher than that of lesions with a diameter of 1~3 cm (16.8%; P＜0.017). The ultrasonic misdiagnosis rate of tumors with ≥2 atypical features (83.5%) was significantly higher than that of tumors without atypical features (0) and with 1 atypical feature (38.6%; P＜0.001). There were 87 complex fibroadenomas and 314 noncomplex fibroadenomas. The misdiagnosis rate of complex fibroadenomas (71.2%) was significantly higher than that of noncomplex fibroadenomas (6.7%; χ²=1.731, P＜0.001). The number of atypical features of complex fibroadenoma was often more than or equal to 2, and the percentage of complex fibroadenomas with more than or equal to 2 atypical features was significantly higher than that of noncomplex fibroadenomas (χ²=2.870, P＜0.001).

The ultrasonic misdiagnosis rate of fibroadenoma is related to the number of atypical features and the size of the mass. Complex fibroadenoma are more likely to show atypical ultrasonic features and be misdiagnosed.