Double Trouble: Lynch Syndrome and KRAS Mutation in a Young Male With Stage IV Colon Adenocarcinoma
Bibliographic record
Abstract
Abstract Title Double Trouble: Lynch syndrome and KRAS Mutation in a Young Male With Stage IV Colon Adenocarcinoma Background Lynch syndrome is a hereditary cancer syndrome caused by germline mutations in mismatch repair (MMR) genes, resulting in microsatellite instability (MSI) and a significantly increased lifetime risk of early-onset colorectal cancer (50%–70%). KRAS mutations, frequently observed in sporadic colorectal cancers, are less commonly associated with Lynch syndrome. Their presence can influence both prognosis and response to targeted therapies, especially anti-epidermal growth factor receptor (EGFR) agents. Case Presentation A 35-year-old man with a history of lumbar radiculopathy and diverticulosis presented in August 2020 with diffuse abdominal pain and altered bowel habits. An abdominal CT scan revealed hepatic metastases, and colonoscopy identified a circumferential, partially obstructing mass in the distal descending colon. Biopsy confirmed a moderately differentiated adenocarcinoma, consistent with colorectal cancer (CRC) with distant metastasis (stage IV). In October 2020, immunohistochemistry demonstrated loss of MLH1, MSH6, and PMS2 expression, consistent with deficient mismatch repair (dMMR) and suggestive of Lynch syndrome. Molecular profiling revealed a concurrent KRAS mutation. The patient was initiated on FOLFOX chemotherapy (5-fluorouracil, leucovorin, and oxaliplatin), administered biweekly, and completed five cycles by November 2020. His current status is unknown, as he was lost to follow-up. Discussion The co-occurrence of dMMR, consistent with Lynch syndrome, and a KRAS mutation presents diagnostic and therapeutic complexity in metastatic CRC. While dMMR or MSI-high (MSI-H) status predicts robust responses to immune checkpoint inhibitors, concurrent KRAS mutations can negate the benefit of anti-EGFR therapies and may influence overall prognosis. In this case, early genomic profiling identified both Lynch syndrome and a somatic KRAS mutation. This guided the decision to initiate FOLFOX chemotherapy, in line with American Society of Clinical Oncology (ASCO) recommendations. However, recent evidence, including the KEYNOTE-177 trial (February 2016-2018) , supports the use of pembrolizumab as first-line therapy in MSI-H/dMMR metastatic CRC, demonstrating superior progression-free survival compared with standard chemotherapy (median, 16.5 vs 8.2 months). Importantly, the presence of a KRAS mutation does not preclude benefit from immune checkpoint inhibitors. Studies demonstrate durable responses in dMMR/MSI-H tumors regardless of KRAS status. Given that KRAS mutations are found in 15% to 35% of Lynch-associated metastatic CRC cases, early and comprehensive molecular testing is essential to guide treatment, assess prognosis, and inform familial risk. This case underscores the evolving role of precision oncology in tailoring individualized treatment by integrating germline and somatic genomic data.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.001 |
| Meta-epidemiology (narrow) | 0.001 | 0.001 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.002 | 0.001 |
| Science and technology studies | 0.002 | 0.001 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.003 | 0.002 |
| Insufficient payload (model declined to judge) | 0.003 | 0.001 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".