Clinical application of next-generation sequencing for the management of desmoid tumors

Rationale: Desmoid tumors are rare myofibroblastic neoplasms characterized by local invasiveness and high rates of recurrence, and sometimes mimic local recurrence of previously resected malignancies. Previous studies have suggested that molecular profiling may be useful for the diagnosis of the tumors and risk stratification. However, the clinical utility of next-generation sequencing (NGS) for the management of desmoid tumors has not been established. Patient concerns: A 42-year-old man visited our clinic for routine follow-up 1 year after left upper lobe lingular segmentectomy for lung adenocarcinoma. Diagnoses: Chest computed tomography showed a pleural mass adherent to the thoracotomy site. Positron emission tomography revealed mildly increased metabolism with a maximal standardized uptake value of 2.7 within the tumor, suggesting local recurrence of the previous neoplasm. Exploratory thoracotomy and en bloc resection of the tumor revealed spindle cells in a massive collagenous tissue consistent with a desmoid tumor. Interventions: NGS was performed to confirm the diagnosis and to identify any genetic alterations that might be relevant to the prognosis of this tumor. The tumor harbored an S45F mutation in CTNNB1 , which has been correlated with a high recurrence rate. Therefore, we performed adjuvant radiotherapy on the resection bed at a dose of 56 Gy. Outcomes: The patients experienced no postoperative or radiotherapy-related complications. Periodic follow-up examinations using computed tomography were performed every 3 months, and no evidence of recurrence of either tumor was observed during the 38 months after the last surgery. Lessons: To the best of our knowledge, this is the first case reporting the clinical application of NGS and aggressive treatment based on the genotyping results for the management of a desmoid tumor. Our case highlights the need to consider desmoid tumors among the differential diagnoses when a pleural mass is encountered at a previous thoracotomy site. More importantly, molecular profiling using NGS can be useful for the establishment of a treatment strategy for this tumor, although further investigations are required.