Defining the incidence and clinical significance of lymph node metastasis in soft tissue sarcoma.
Introduction: The incidence and clinical significance of lymph node metastasis (LNM, N1) in soft tissue sarcoma (STS) is unclear. Recent studies have focused on extremity/trunk STS (ETSTS). We sought to define the subgroup of patients with LNM at sarcoma diagnosis across all disease sites and histologies.
Methods: We identified and categorized 89,870 STS patients from the National Cancer Data Base (1998-2012) by nodal stage. Pathologically confirmed LNM (pN1) were identified in 1404 patients; 1750 had clinically suspicious but not pathologically confirmed LNM (cN1). Survival analyses were performed by Kaplan-Meier method.
Results: Of 3154 patients (3.5%) with pN1 or cN1 LNM at presentation, 1310 had synchronous distant metastasis (M1). LNM affected a small proportion of patients (5.8% head/neck, 5.3% intrathoracic, 5.1% intra-abdominal, 2.0% ETSTS). Angiosarcoma (6%), epithelioid (13%), clear cell (16%), and small cell sarcoma (19%) had the highest incidence of LNM, although liposarcoma, fibrous histiocytoma, and leiomyosarcoma accounted for the greatest number of LNM patients. For pN1M0 disease, median overall survival (OS) was 28.2 months, varying by histology. Among patients with pN1M0 STS, angiosarcoma, clear cell sarcoma, leiomyosarcoma, and fibrous histiocytoma were associated with worse median OS (19.4, 23.8, 27.1, and 29.3 months) compared to epithelioid sarcoma and liposarcoma (49.6 and 56.0 months, p < 0.001).
Conclusion: Despite clinical suspicion, pathologic LN evaluation in STS is inconsistently performed. LNM occurs across anatomic disease sites and is unevenly distributed across histologies. Although M1 disease portends poor prognosis regardless of LN status, LNM predicts worse OS in a histology-dependent manner in M0 disease.