Objective The aim of this study was to investigate the clinicopathological and ultrasonographic characteristics of metaplastic breast carcinoma（MPBC）and differential diagnosis from invasive ductal breast carcinoma of no special type (IDC-NOS) selected at the same time randomly. Methods We retrospectively reviewed the clinicopathological and ultrasonographic characteristics of 33 patients with MPBC and 66 patients with IDC-NOS confirmed by pathology in our hospital from January 2015 to December 2020. Results The most common features of MPBC observed in ultrasound were as follows:hypoechoic mass

indistinct margin

irregular shape

Adler II～III

posterior acoustic enhancement.The rates of axillary nodal involvement were lower than that of IDC-NOS. Squamous cell carcinoma was the common pathological type of MPBC. Triple negative type was the main molecular subtype of pathology. The average score of Ki-67 （59.4%）was higher than that of IDC-NOS (37.5%).There were no significant differences in clinical manifestations (P>0.05). Conclusion Compared with IDC-NOS

MPBC can show the differential clinicopathological and ultrasonographic characteristics.