Extraskeletal Ewing's sarcoma: outcomes and CT features of endoceliac lesions

Background: Extraskeletal Ewing's sarcoma (EES) is one kind of rare malignant tumour which is always misdiagnosed preoperatively, especially for lesions located at endoceliac sites. This study analyse the clinicopathological features and outcomes of EES patients. The basic imaging characteristics of endoceliac lesions are also summarized. Methods: This study involved EES patients admitted to our centre between January 2000 and January 2020. Clinical data from patients with EES (n=25) and computed tomography (CT) features from endoceliac EES patients with available CT data (n=8) were retrospectively reviewed. Results: The sample comprised 18 males and 7 females with a median age of 30 years (range, 1-72 years). Seven patients had EES originating from surface sites and 18 had EES originating from endoceliac sites. The median tumour size was 8.0 cm (range, 2.5-17.0 cm). In total, 20% of patients had distant metastasis at diagnosis. In the univariate analyses, tumour size >8 cm, non-surgical treatment, and regional lymph nodes metastasis were risk factors for poor prognosis of EES. In the multivariate analysis, patients with larger tumour size and regional lymph node metastasis were independent predictors of overall survival (OS). Endoceliac EES cases frequently exhibited lobulated contour (87.5%), absence of calcification (75%), severe necrosis or cystic degeneration (75%), heterogeneous enhancement (100%), moderate enhancement (75%), ill-defined borderline (62.5%), and organ invasion (75%). Half of the patients with endoceliac EES had CT features of lymphadenopathy. Conclusions: Comprehensive understanding of the clinicopathological and imaging features of EES is beneficial for diagnosis, development of therapeutic strategies, and accurate prediction of prognosis for this rare malignant tumour.