In lung adenocarcinoma, the lepidic growth pattern refers to tumor cells growing along pre-existing alveolar walls without stromal invasion. This pattern has the BEST prognosis. Which molecular profile is MOST likely to be found in a lepidic-predominant adenocarcinoma in a young non-smoking East Asian woman?
- A KRAS mutation (codon 12)
- B BRAF V600E mutation
- C EGFR activating mutation (exon 19 deletion or exon 21 L858R) ✓
- D ALK fusion gene rearrangement
Explanation
EGFR activating mutations (exon 19 deletion and exon 21 L858R together account for ~85-90% of EGFR mutations) are the most common druggable driver mutations in lung adenocarcinoma, occurring in ~50% of East Asian women who are never-smokers. They are associated with well-differentiated adenocarcinoma including lepidic patterns and confer sensitivity to EGFR tyrosine kinase inhibitors (gefitinib, erlotinib, osimertinib). KRAS mutations are more common in smokers, western populations. ALK fusions (EML4-ALK) also occur in young non-smokers but are less frequent than EGFR mutations and are associated with signet-ring features.
Reference: Robbins & Cotran Pathologic Basis of Disease, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.