A 35-year-old woman undergoes core biopsy of a palpable breast mass. Histology shows tubular carcinoma — small, well-formed tubules with open lumens, low nuclear grade, and no stromal desmoplasia. Which is the characteristic IHC profile expected in this special type breast carcinoma?

• A ER+, PR+, HER2−, low Ki-67; luminal A subtype ✓
• B ER−, PR−, HER2− (triple negative), with basal CK5/6 and EGFR positivity
• C ER−, PR−, HER2+++ with chromosome 17 amplification
• D ER+, PR−, HER2+, intermediate Ki-67

Explanation

Tubular carcinoma of the breast is a special type carcinoma with excellent prognosis (nearly 100% 10-year survival). It is almost universally ER+/PR+/HER2−, classifying it as luminal A molecular subtype with low Ki-67. The tubule formation with angular, irregular open lumens lined by single-layered cells (without myoepithelial cells), set in a desmoplastic stroma, is pathognomonic. The excellent prognosis means sentinel lymph node biopsy and adjuvant chemotherapy may be avoidable; endocrine therapy alone is typically sufficient. Triple-negative breast cancer is more aggressive and associated with BRCA1 mutations.

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

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Written and medically reviewed by the StethoPrep medical team.