## RAS Oncogene Prevalence in Cancer **Key Point:** RAS mutations are the single most common oncogenic alteration across all human malignancies, found in approximately 30–50% of cancers globally. ### RAS Mutation Frequency by Cancer Type | Cancer Type | RAS Mutation Frequency | Notes | | --- | --- | --- | | Pancreatic adenocarcinoma | 75–90% | Highest frequency | | Colorectal cancer | 40–50% | Common in adenomas | | Lung cancer (NSCLC) | 20–30% | Especially adenocarcinoma | | Melanoma | 15–25% | Varies by subtype | | Acute myeloid leukemia | 20–30% | FLT3 and NPM1 also common | | Thyroid cancer | 20–40% | Papillary and follicular types | **High-Yield:** The 30–50% figure is a testable fact in NEET PG. RAS is the most frequently mutated oncogene, followed by TP53 (most frequently mutated tumor suppressor). ### Why RAS Is So Commonly Mutated 1. **Three isoforms** — KRAS, NRAS, HRAS provide redundancy; mutation of any one can drive cancer 2. **Single amino acid substitution** — Point mutations at codons 12, 13, or 61 cause constitutive GTPase activity 3. **Early event** — RAS mutations often occur early in carcinogenesis, especially in colorectal adenoma-carcinoma sequence 4. **Broad tissue distribution** — RAS is expressed in nearly all cell types **Mnemonic:** RAS = Remarkably Altered in ~50% of cancers (remember the 30–50% range).
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