Differentiation of benign and metastatic lymph nodes in soft tissue sarcoma

Introduction: Lymph node metastasis (LNM) occurs in less than 5% of soft tissue sarcoma (STS) patients and indicates an aggressive course of disease. Suspicious lymph nodes in staging imaging are a frequent matter of discussion in multidisciplinary tumor boards. Predictive markers are needed to enable stratification and improve treatment of STS patients. Materials and Methods In this study, 56 STS patients with radiologically suspicious and subsequently histologically examined lymph nodes (LN) were reviewed. Patients with benign (n = 26) and metastatic (n = 30) LN were analyzed with regard to clinical, laboratory and radiological parameters. Results Short axis diameter (SAD) and long axis diameter (LAD) of LN were significantly larger in patients with LNM (median 22.5 vs. 14mm, p < 0.001 and median 29.5 vs. 21mm, p = 0.003, respectively). In addition, presence of central necrosis and high maximal standardized uptake value (SUVmax) in FDG-PET-CT scan were significantly associated with LNM (60 vs. 11.5% of patients, p < 0.001 and median 8.59 vs. 3.96, p = 0.013, respectively). With systemic therapy, a slight median size regression per time was observed in both metastatic and benign LN. Serum LDH and CRP levels were significantly higher in patients with LNM (median 247 vs. 187.5U/l, p = 0.005 and 1.5 vs. 0.55mg/dl, p = 0.039, respectively). Conclusion This study shows significant associations between LNM and imaging features as well as laboratory parameters of STS patients. The largest SAD, SUVmax in FDG-PET-CT scan, the presence of central necrosis, and high serum LDH level are the most important parameters to distinguish benign from metastatic LNs.