KRAS mutations are more likely found in all of the following except...

• A. Adenocarcinomas
• B. Smokers
• C. NSCLC
• D. Caucasians

Answer: (C)

KRAS mutations in lung cancer are most strongly tied to a specific histology and smoking history. They are commonly found in adenocarcinomas, especially in patients with a history of smoking, and they occur more often in Caucasians than in some other populations. Within non-small cell lung cancer, this pattern is most relevant to adenocarcinoma, not to the entire NSCLC category, which also includes histologies like squamous cell carcinoma where KRAS mutations are less common. Because of that broader NSCLC group, saying KRAS mutations are more likely across all NSCLC isn’t as accurate as the stronger associations with adenocarcinoma, smoking, and Caucasian ethnicity. So the statement that KRAS mutations are more likely in NSCLC as a whole is the exception, while the other associations fit the established pattern.