A 62-year-old woman is diagnosed with a 1.5 cm invasive lobular carcinoma of the left breast, ER-positive, PR-positive, HER2-negative, clinically node-negative. Which statement about invasive lobular carcinoma compared to invasive ductal carcinoma is correct?
- A It is more likely to be unilateral and form a discrete palpable mass
- B It is more likely to be HER2-positive
- C It has a higher rate of bilateral involvement and may show diffuse infiltrative growth ✓
- D It is less likely to be hormone receptor-positive
Correct answer: C. It has a higher rate of bilateral involvement and may show diffuse infiltrative growth
Explanation
Invasive lobular carcinoma is characterized by loss of E-cadherin (CDH1), leading to single-file infiltrative growth, bilateral involvement in 20-30% of cases, and diffuse rather than discrete mass formation. It is more frequently ER/PR-positive, not HER2-positive. IDC forms discrete masses and is more common unilaterally.
Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.
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