A previously healthy 16-year-old male presented with symptoms that led clinicians to perform an appendectomy for suspected acute appendicitis. Postoperative persistence of bowel obstruction prompted cross-sectional imaging. CT imaging identified a mass in the descending colon causing obstruction, and the patient required an emergency Hartmann's procedure. The clinical course moved rapidly from presumed benign appendicitis to an urgent oncologic surgical intervention.
This sequence of events illustrates a common pitfall: colorectal malignancy can masquerade as routine surgical presentations in adolescents. The authors reported that imaging and intraoperative findings necessitated definitive resection, and that pathology specimens were subsequently processed for histology and immunohistochemistry.
Histopathological examination identified mucinous adenocarcinoma of the descending colon. Tumor staging was reported as pT4N0M0, with documented vascular invasion. Immunohistochemistry showed loss of MSH2/MSH6 protein expression while MLH1 and PMS2 expression were retained, a pattern consistent with dMMR and highly suggestive of Lynch syndrome in the clinical context.
Molecular testing detected a KRAS mutation; the report specified absence of NRAS alterations. The source did not provide detailed mutation codons, allele frequencies, or the technical platform used for sequencing. The authors explicitly stated that germline genetic testing was unavailable, so a definitive molecular diagnosis of Lynch syndrome could not be established in this patient.
Several adverse prognostic features influenced the multidisciplinary treatment decision. The tumor was T4 and had caused acute intestinal obstruction. Vascular invasion was present on pathology. Morphology was mucinous, and the patient’s age—adolescent—was an additional clinical concern. The study team reported that these combined high-risk characteristics prompted selection of an intensive adjuvant approach.
The presence of dMMR/MSI-H biology was documented, but the case report did not specify whether MSI testing beyond immunohistochemistry (for example, PCR‑based MSI panels) was performed. The authors emphasized that comprehensive molecular profiling and routine MMR/MSI evaluation are essential in young-onset colorectal cancer to identify patients who may have hereditary cancer syndromes and thus need genetic counseling.
The patient received adjuvant combination chemotherapy with FOLFOX, administered as 12 cycles. The source named the regimen class (fluorouracil/leucovorin plus an oxaliplatin-containing agent) but did not provide dosing schedules, dose modifications, or specific toxicity grading data. According to the authors, the treatment course was well tolerated.
The decision to use adjuvant FOLFOX in a young patient with dMMR/MSI-H disease and multiple high-risk features illustrates individualized multidisciplinary decision-making; the report described clinical judgment directed by stage and pathologic risk rather than by a single biomarker alone.
Authors reported that the patient remained disease-free for more than five years following completion of adjuvant chemotherapy. The source did not outline the surveillance protocol (imaging intervals, colonoscopic schedule, tumor marker monitoring) used during follow-up. No recurrent disease or treatment-related late effects were detailed in the abstract.
Sustained remission in this single patient aligns with the authors’ framing that tailored, aggressive management can produce favorable outcomes in selected young patients, but the report refrains from generalizing beyond this case.
This report is limited by its single‑case design; authors explicitly noted that their observations are confined to one patient. Germline genetic testing was not available, so the clinical suggestion of Lynch syndrome based on loss of MSH2/MSH6 could not be molecularly confirmed. The source did not report detailed sequencing methodology, specific KRAS variant information, or a standardized surveillance schedule.
Unanswered clinical questions documented by the authors include the absence of definitive germline confirmation and the limited generalizability of a single-case outcome. These gaps restrict interpretation of how broadly similar management would apply to other adolescents with MSI-H/dMMR colorectal cancer.
Clinicians reviewing this case should note the described approach: emergent resection for obstruction, pathologic and immunohistochemical assessment for MMR/MSI status, molecular profiling that identified KRAS mutation, and adjuvant FOLFOX for multiple high‑risk features—followed by a reported disease‑free interval exceeding five years—while recognizing the report’s inherent limitations and missing germline data.