CTNNB1 and spindle cell neoplasm: Previous studies have reported that the presence of CTNNB1 mutations can be a diagnostic marker for desmoid tumors among spindle-cell tumors, and a specific genotype, S45F mutation, is associated with a high recurrence rate compared to other genotypes.[7–9,11] Therefore, we were able to confirm the patient's diagnosis and predict the aggressive behavior of this tumor.