Staging has an important role in determining the most effective treatment for soft tissue sarcoma. Clinical staging involves magnetic resonance imaging (MRI) or computed tomography (CT) of the primary tumor area and a chest CT to look for metastasis to the lung (the most common site of distant spread). An abdominal CT scan is done in the case of retroperitoneal sarcomas because the liver may be the site of initial clinical metastasis for these tumors.
The stage is determined by the size of the tumor, the histologic grade, and whether there is spread to lymph nodes or distant sites. Intracompartmental or extracompartmental extension of extremity sarcomas is also important for surgical decision making. For complete staging, a thorough review of all biopsy specimens (including those from the primary tumor, lymph nodes, or other suspicious lesions) is essential. CT scan of the chest is recommended for sarcomas larger than 5 cm (T2) or with moderate to poor differentiation (grades 2–4). Nodal involvement is rare, occurring in less than 3% of patients with sarcoma.
Lymph node involvement in soft tissue sarcomas of adulthood is rare but is somewhat more frequent in some subtypes (e.g., rhabdomyosarcoma, vascular sarcomas, clear cell sarcomas, and epithelioid sarcomas) when they are high grade. Because treatment decisions are predicated on pathology staging, patients should be staged before, and again after, any neoadjuvant therapy. The assessment of tumor grade can be affected in either direction, but more frequently decreased because of differential cellular loss related to the neoadjuvant chemotherapy or radiation. Grade, which is based on cellular differentiation, mitotic rate, and extent of necrosis, should be recorded for all soft tissue sarcomas. A three-grade system (G1–G3) is preferred. (See Table 4 below).
The American Joint Committee on Cancer (AJCC) has designated staging by the four criteria of tumor size, nodal status, metastasis, and grade (TNMG). The characteristic molecular markers of some sarcomas are not formally incorporated in the staging system pending further evaluation of their impact on prognosis. Recurrent sarcomas are restaged using the same system as for primary tumors with the specification that the tumor is recurrent.
Definitions of TNM and Grade