Molecular subtypes and imaging phenotypes of breast cancer

Abstract

During the last 15 years, traditional breast cancer classifications based on histopathology have been reorganized into the luminal A, luminal B, human epidermal growth factor receptor 2 (HER2), and basal-like subtypes based on gene expression profiling. Each molecular subtype has shown varying risk for progression, response to treatment, and survival outcomes. Research linking the imaging phenotype with the molecular subtype has revealed that non-calcified, relatively circumscribed masses with posterior acoustic enhancement are common in the basal-like subtype, spiculated masses with a poorly circumscribed margin and posterior acoustic shadowing in the luminal subtype, and pleomorphic calcifications in the HER2-enriched subtype. Understanding the clinical implications of the molecular subtypes and imaging phenotypes could help radiologists guide precision medicine, tailoring medical treatment to patients and their tumor characteristics.

Keywords: Breast neoplasms; Diagnosis; Gene expression profiling; Ultrasonography.

Fig. 1.. A 59-year-old woman with a basal-like breast cancer.

A. Mammography shows an irregular mass with an indistinct margin without calcifications. B. Sonograms shows an irregular mass with a circumscribed margin and a posterior acoustic enhancement. C. Gadolinium-enhanced T1-weighted magnetic resonance (MR) image shows an irregular mass with rim-enhancement. D. T2-weighted MR image shows an irregular mass with internal high signal intensity. Histopathology revealed an invasive ductal carcinoma with high histologic grade. Immunohistochemistry analysis showed estrogen receptor-negative, progesterone receptor-negative, human epidermal growth factor receptor 2-negative, cytokeratin 5/6-positive, and Ki-67-30% positive.

Fig. 2.. A 45-year-old woman with a luminal A-like breast cancer.

A. Mammography shows a spiculated mass with calcifications. B. Sonogram shows an irregular mass with spiculated margin and posterior acoustic shadowing. Histopathology revealed an invasive ductal carcinoma with low histologic grade. Immunohistochemistry analysis showed estrogen receptor-85% positive, progesterone receptor-90% positive, and human epidermal growth factor receptor 2-negative.

Fig. 3.. A 35-year-old woman with a human epidermal growth factor receptor 2 (HER2)-positive breast cancer.

A. Mammography shows segmental, pleomorphic, linear branching microcalcifications. B. Songogram shows an ill-defined, irregular mass with calcifications within surrounding ductal changes. Histopathology revealed an invasive ductal carcinoma with high histologic grade. Immunohistochemistry analysis showed estrogen receptor-negative and progesterone receptor-negative. HER2 was positive on fluorescence in situ hybridization.