Which molecular subtype is described as the most common, slowest-growing, and most treatable, and typically hormone receptor-positive?

• A. Luminal B
• B. HER2-Enriched
• C. Basal
• D. Luminal A

Answer: (D)

Understanding breast cancer subtypes hinges on hormone receptor status, HER2 expression, and how quickly the cancer tends to grow. The profile described—hormone receptor-positive, HER2-negative, and low proliferation—best fits Luminal A. This subtype tends to grow slowly, is the most common form, and responds very well to endocrine therapies that block estrogen signaling, making it the most treatable among the breast cancer subtypes. In contrast, Luminal B is ER-positive but has higher proliferation or may be HER2-positive, making it more aggressive and often requiring additional treatments. HER2-Enriched usually lacks hormone receptors and relies on HER2-targeted therapies, with a typically more aggressive course, while Basal-like is often triple-negative and harder to treat due to fewer targeted options.