Infiltration of the oedema tail with tumour cells in patients with a soft-tissue sarcoma – the predisposing factors and clinical relevance

Aims: Some histological subtypes of soft-tissue sarcoma have an oedema tail evident on T2 hyperintensity in MRI scans at the time of presentation. The clinical and prognostic relevance of the infiltration of the oedema tail with tumour cells is not clear. The aim of this study was to determine the rate of contamination of the oedema tail with tumour cells in a series of sarcomas, the variables that affect the presence of tumour cells in the oedema, and the oncological relevance of the infiltration. Methods: A total of 67 patients who had a primary appendicular soft-tissue sarcoma with an oedema tail at the time of presentation were treated in our tertiary referral centre between June 2017 and January 2022; 21 were excluded and 46 were included in this prospective study. We recorded epidemiological, radiological, and histological variables and investigated their correlation with infiltration of the oedema by tumour cells. Preoperative MRI scans were used to determine the presence and length of the oedema tail as assessed by an expert radiologist. The oedema was defined as a high-intensity signal in the edges of the sarcoma on a T2 STIR sequence. The oedema tail and the margins of the resection were measured and evaluated by an expert pathologist based on preoperative MRI scans. The overall survival and local recurrence-free survival were determined at a median follow-up of 36.8 months (IQR 17.4 to 50.7). Four patients were lost to follow-up. Results: A total of 12 of the 46 patients (26%) showed infiltration into the oedema by > 2 mm from the pseudocapsule. The mean distance between the pseudocapsule and the tumour cells in oedema was 20 mm (2 to 40). The size and superficial location were independent variables for infiltration by tumour. The presence of tumour cells in the oedema was significantly associated with the overall survival (hazard ratio (HR) 0.299 (95% CI 0.104 to 0.999); p = 0.042). Conclusion: The mean length of the oedema tail was 20 mm (2 to 40) and was infiltrated with tumour cells in 12 patients (26%). The overall survival was significantly poorer in those with, compared with those without, tumour cells in the oedema. Future studies should focus on the risk factors for the infiltration of the oedema with tumour cells, the association between the presence of infiltration and radiotherapy and chemotherapy, and whether it affects the prognosis in these patients.