Imaging features of SMARCA4-deficient thoracic sarcomas: a multi-centric study of 21 patients.

OBJECTIVES: SMARCA4-deficient thoracic sarcoma (SMARCA4-DTS) is a recently identified aggressive subtype of sarcoma. The aim of this study was to characterize the CT imaging features of SMARCA4-DTS.

METHODS: From June 2011 to May 2017, 21 adult patients with histologically proven SMARCA4-DTS were identified in the radiological database of 2 French sarcoma reference centers with at least one chest CT scan available. The locations, sizes, heterogeneity, margin definitions, and local extensions of the tumors were reported together with their impact on surrounding organs and regional and distant metastases. Pathological findings, molecular analyses, and patients' outcomes were retrieved.

RESULTS: Of the 21 included patients (median age 48, range 30-74), 18 (85.7%) were male and 18 (85.7%) had a smoking history. Four main radiological patterns were identified depending on the location of the main tumor burden: mediastinal (n = 13), pleural (n = 6), cervical (n = 1), and retroperitoneal (n = 1). Median size was 120 mm (range 46-266). Characteristic CT imaging features of primary tumors included ill-defined margins (n = 21), heterogeneous enhancement after injection (n = 20), multi-compartment extension from mediastinum to lung apex, pleura, or neck (n = 20), compressive effect responsible for atelectasis (n = 11), vascular encasement (n = 16-5 superior vena cava syndrome), and esophagus invasion (n = 5). Primary tumors showed strong 18F-FDG avidity in eight patients with PET-CT. Necrotic lymphadenopathies were found in 19 patients, with a surrounding infiltrate in 13 patients. Metastatic locations at baseline mainly involved adrenal (n = 10), lung (n = 6), and bone (n = 5). Median overall survival was 5 months (range 1-13).

CONCLUSION: Most SMARCA4-DTS present with compressive and infiltrative chest masses with ill-defined necrotic lymphadenopathies. The diagnosis of SMARCA4-DTS should enter in the differentials of the radiologist, especially in the case of a rapidly evolving thoracic mass in young smoking males.

KEY POINTS: • SMARCA4-DTS is a very aggressive poorly differentiated sarcoma with a predilection for young and middle-aged adult male smokers. • SMARCA4-DTS, which is mostly located in the chest cavity, can compress and infiltrate all adjacent organs leading to superior vena syndrome, lung atelectasis, epiduritis, spinal cord compression, and esophagus invasion. • SMARCA4-DTS typically demonstrates several ill-defined necrotic lymphadenopathies spreading in axillar, subclavian, cervical, mediastinum, and retroperitoneum.