Grading and Staging

Abstract

Grading is applied only to malignant tumors. Usually, a scale of 1–4 is used to grade malignant tumors based on their histological resemblance to “normal counterparts.” Conventional osteosarcomas are high-grade tumors. Chondrosarcoma is graded on a scale of 1–3. Ewing’s sarcoma and mesenchymal chondrosarcoma are always regarded as high-grade tumors. Malignant lymphoma, myeloma, chordoma, and adamantinoma are not graded because grading has not been proved to correlate with clinical behavior.

Staging is the process of classifying a tumor with respect to its degree of differentiation as well as its local and distant spread in order to estimate the prognosis of the patient. The Musculoskeletal Tumor Society adopted staging systems for both benign and malignant bone tumors. Benign lesions are graded 1 or 2 according to the degree of local aggressiveness. A surgical staging system for malignant lesions is accomplished by assessment of the surgical grade, low or high grade; the local extent, intra- or extracompartmental; and the presence or absence of regional or distant metastases. Four types of surgical margin are also recognized: intralesional margin, marginal margin, wide margin, and radical margin.