Genotype-guided conservative management of mesenteric desmoid tumors: A case report of intermediate-region APC mutations

Rationale: Desmoid tumors (DTs) exhibit highly variable behavior, making management challenging. Specific adenomatous polyposis coli (APC) gene mutation sites are recognized as key prognostic markers, potentially enabling genotype-guided strategies to avoid overtreatment. Patient concerns: We present 2 symptomatic patients with familial adenomatous polyposis-associated mesenteric DTs. Patient 1 was a 46-year-old female with a large, symptomatic pelvic mass. Patient 2 was a 26-year-old male with multifocal recurrent disease, including a symptomatic abdominal wall lesion. Diagnoses: Diagnosis was confirmed by imaging and histopathology. Genetic sequencing identified intermediate-region APC mutations: a somatic c. 1821T > A (p. Cys607Ter) mutation in patient 1 and a c. 3183₃187delACAAA (p. Gln1062Ter) mutation in patient 2. Interventions: Management was stratified by genotype. Given the indolent-predicting mutations, patient 1 was managed with active surveillance alone. For patient 2, the symptomatic abdominal wall lesion was resected, and low-intensity systemic therapy (tamoxifen and celecoxib) was initiated for residual mesenteric disease. Outcomes: At 5-year follow-up, patient 1’s tumor showed >50% volume reduction with symptom alleviation. Patient 2 achieved sustained disease stability in all lesions at 3-year follow-up, with partial symptom remission. No significant treatment-related adverse events occurred. Lessons: Intermediate-region APC mutations (e. g. , codons 607 and 1062) predict an indolent course in mesenteric DTs. Comprehensive APC genotyping at diagnosis enables risk-adapted management, permitting safe use of conservative strategies (active surveillance/low-intensity therapy) and helps avoid unnecessary aggressive interventions. This underscores the critical role of molecular profiling in personalizing DT care.