Stage 1 Colon Cancer at 37 Prompts BRCA2 Testing Despite Limited Evidence Linking Mutation to Colorectal Risk

Marisa Stachelski experienced progressive abdominal bloating, pain, and visible rectal bleeding in 2022. A dietitian-ordered G-MAP stool test detected occult blood, leading to colonoscopy that identified a cancerous polyp. Surgical resection confirmed stage 1 disease with no adjuvant therapy required. Genetic testing performed one week post-diagnosis revealed a BRCA2 pathogenic variant, prompting risk-reducing mastectomy and salpingectomy plus intensified surveillance.

Observational data show BRCA2 carriers have modestly elevated colorectal cancer risk (standardized incidence ratio 1.5-2.0 in some cohorts), yet NCCN guidelines do not list isolated early-onset colon cancer as a routine indication for BRCA testing. The case illustrates how clinician discretion and patient request can trigger panels that uncover incidental actionable variants. Family history of paternal pancreatic cancer supplied the plausible transmission route, though testing of relatives remains incomplete.

This single-patient narrative cannot establish causality between BRCA2 and colon cancer nor quantify screening benefit. Larger prospective registries are needed to determine whether BRCA2 status meaningfully changes colorectal surveillance intervals beyond standard post-cancer protocols. Current evidence supports BRCA2 testing primarily when breast, ovarian, or pancreatic cancers cluster in families.