A 28-year-old woman presents with a 3 cm breast mass. Core biopsy shows invasive carcinoma with a syncytial growth pattern, high-grade nuclei, prominent lymphoplasmacytic infiltrate, and pushing margins. E-cadherin is positive. Which molecular subtype is most likely?

• A Basal-like ✓
• B Luminal B
• C HER2-enriched
• D Luminal A

Explanation

Medullary carcinoma is morphologically defined by syncytial growth, high-grade nuclei, and lymphoplasmacytic infiltrate. It is almost always triple-negative and falls into the basal-like molecular subtype. Luminal D and B tumors are ER-positive and have lower nuclear grades. HER2-enriched tumors lack the syncytial pattern and lymphoid infiltrate typical of medullary carcinoma.

Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.