Introduction
Non-rhabdomyosarcoma soft tissue sarcomas (NRSTS) are rare childhood malignancies that account for 3-7% of pediatric cancers annually.1,2 Comprising over 50 histological subtypes, NRSTS have a wide variety of clinical presentations and treatment pathways. Across all histological subtypes, overall survival (OS) is associated with tumor grade, tumor size, evidence of metastasis, and extent of surgical resection.3 Studying outcomes for individual subtypes is challenging due to low incidence. As a result, pediatric providers rely on results from adult literature as well as pediatric studies that aggregate subtypes by similar clinical or genetic features.3-5
One common grouping of NRSTS is by propensity for early lymph node metastasis. Most NRSTS rarely metastasize to lymph nodes4,6, but higher risk NRSTS subtypes historically included clear cell sarcoma of soft tissue (CCS), epithelioid sarcoma, and synovial sarcoma.7 Over the past two decades, large database studies in adults and single-center studies in children have corroborated lymph node metastases are prevalent in up to 30% of patients with CCS and epithelioid sarcoma.4,6,8-10Conversely, synovial sarcoma in adults is now understood to have an incidence of lymph node metastasis as low as 4.2%6,9, but this association has not been well-studied in children.
Understanding the incidence of lymph node involvement in children with NRSTS tumors is important, as both the adult and pediatric literature support an association between lymph node metastasis and inferior OS across all NRSTS subtypes.3,6,9,11 Additionally, patients identified with lymph node metastasis can receive targeted radiation or completion lymphadenectomy to reduce tumor recurrence.12 However, physicians must weigh suspicion for lymphatic involvement against the risks associated with sampling procedures, including wound infection and lymphedema.13 Current recommendations include routine lymph node pathologic evaluation in children with CCS and epithelioid sarcoma. However, further data are needed to understand the impact of lymph node sampling on survival in pediatric patients.
We sought to clarify trends of lymph node metastasis in pediatric patients with CCS, epithelioid, and synovial sarcoma from a nationwide database. We also explored lymph node sampling practices for these NRSTS subtypes over the past decade. Finally, we examined the association between lymph node sampling, lymph node metastasis, and overall survival in this population.