Staging and Grading Systems for Childhood Soft Tissue Sarcoma
Clinical staging has an important role in predicting the clinical outcome and determining the most effective therapy for pediatric soft tissue sarcomas (STSs). As yet, there is no well-accepted staging system that is applicable to all childhood sarcomas. The system from the American Joint Committee on Cancer (AJCC) that is used for adults has not been validated in pediatric studies.
Although a standardized staging system for pediatric nonrhabdomyosarcomatous STS does not exist, the last Children's Oncology Group (COG) trial used the sixth edition AJCC cancer staging manual for STSs (with central pathology review) (see Tables 3–6 below).
Two systems are currently in use for staging pediatric nonrhabdomyosarcomatous STS tumors.
- Surgico-pathologic staging system: The surgico-pathologic staging system used by the Intergroup Rhabdomyosarcoma Study (see below) is based on the amount, or extent, of tumor that remains after initial surgery and whether the disease has metastasized.
- TNM staging system: The other system typically used to stage pediatric soft tissue tumors is the TNM system of the International Union Against Cancer. Staging is based on the extent of the tumor (T), the extent of spread to the lymph nodes (N), and the presence of metastasis (M).
Intergroup Rhabdomyosarcoma Study Staging System
- Group I: Localized tumor, completely resected with histologically negative margins.
- Group II: Grossly resected tumor with microscopic residual tumor at the margin(s) and/or extension into regional lymph nodes.
- IIA: Localized, grossly resected tumor with microscopic residual disease.
- IIB: Regional disease with involved nodes completely resected with no microscopic disease. The most proximal (to the patient, most distal to the tumor) regional lymph node must be negative.
- IIC: Regional disease with involved nodes grossly resected but with evidence of residual microscopic disease at the primary site and/or histologic involvement of the most proximal regional lymph node in the dissection.
- Group III: Localized tumor, incompletely resected, or biopsy only, with gross residual tumor.
- Group IV: Any localized or regional tumor with distant metastases present at the time of diagnosis. This includes the presence of malignant cells in effusions (pleural, peritoneal) and/or cerebrospinal fluid (rare).
TNM Staging System
The AJCC has designated staging by the four criteria of tumor size, nodal status, histologic grade, and metastasis.