Abstract:Objective: To investigate the relationship between the imaging features and the clinicopathological characteristics of non-mass ductal carcinoma in situ (DCIS) and to analyze their correlation with molecular subtypes. Methods: This study selected 100 patients with non-mass DCIS who underwent surgical treatment at our hospital from June 2020 to June 2021.The patients were classified into four types (Type I:31 cases,Type Ⅱ:15 cases,Type Ⅲ:43 cases,and Type Ⅳ:11 cases) based on ultrasound findings.Immunohistochemistry was used to evaluate the positive expression of estrogen receptor (ER),progesterone receptor (PR),human epidermal growth factor receptor 2 (HER2),and Ki-67.Patients were categorized into Luminal A and Luminal B molecular subtypes according to the St.Gallen standard. Results: Type I exhibited thickened and tortuous ducts with low echogenicity within the lumen.Type Ⅱ displayed patchy hypoechoic areas with indistinct boundaries in the breast.Type Ⅱ showed lamellar hypoechoic areas with unevenly distributed punctate strong echoes in the breast.Type Ⅳ presented disordered glandular structures with distorted architecture.There were no statistically significant differences in age,tumor diameter,menstrual status,lesion location,and clinical symptoms among patients with Type I,Type Ⅱ,Type Ⅲ,and Type Ⅳ non-mass DCIS (P>0.05).However,as the ultrasound classification level increased,nuclear grade also increased (P<0.05).There were no significant differences in the positive expression of ER,PR,Ki-67 levels among Type I,Type Ⅱ,Type Ⅲ and Type Ⅳ non-mass DCIS patients (P>0.05).But,there was a significant difference in HER2 positive expression between Type I and Type Ⅱ,with Types Ⅲ and Ⅳ showing a higher HER2 positive expression (P<0.05).There was no significant difference in HER2 positive expression between type I and type II patients (P>0.05). Compared to type I, type III and type IV showed higher HER2 positive expression (P<0.05). Type III had higher HER2 positive expression compared to type II, but the difference with type IV was not statistically significant (P>0.05). The distribution of Luminal A and Luminal B subtypes increased in type III compared to type I (P<0.05), and the distribution of Luminal B subtype increased in type IV compared to type I (P<0.05), while the difference in Luminal A subtype was not statistically significant (P>0.05). Conclusion: Patients with non-mass DCIS mainly exhibited calcification on ultrasound.Patients with structural disorders had higher nuclear grades and more HER2 positive expression.These factors were correlated with a decrease in Luminal A subtype and an increase in Luminal B subtype.