Morphology to molecular subtyping: Retrospective study to correlate the molecular subtypes of breast cancer with mammography and ultrasound imaging features

Objectives To identify the imaging features of malignant breast masses on mammogram and ultrasound. To correlate the morphological features of these masses with immunohistochemistry markers for different molecular subtypes of breast cancers. Materials and Methods A retrospective study was conducted including 192 patients from April 2018 to March 2022. Based on IHC, biopsy-proven breast cancers were divided into 4 subtypes (Luminal A, Luminal B, HER2, and TNBC). Mammogram and Ultrasound features were independently studied according to ACR BI-RADS Lexicon criteria. Statistical analysis was performed using the Chi-square and Fisher’s exact test with significance at p < 0.05. Results Luminal A cases are predominantly irregular hypoechoic anti-parallel masses with spiculated margins and posterior acoustic shadowing. Luminal B cases are commonly irregular hypoechoic anti-parallel masses with spiculated or micro-lobulated margins and no specific posterior features. HER2 cases are predominantly irregular heterogeneous anti-parallel masses with micro-lobulated margins, mixed posterior features, and intra-lesional calcifications. TNBC cases are relatively round to oval wellcircumscribed masses with parallel orientation and posterior acoustic enhancement. Lymphadenopathy, Oedema, and duct involvement were more commonly seen in HER2 and TNBC subtypes. A distinctive feature in our study was a cystic component within TNBC. Conclusion Each molecular subtype of breast cancer has certain unique morphological features on imaging that can be used to aid the diagnosis and management of breast carcinoma.