Grading of bone tumors.

Malignant tumors are graded based on the resemblance of the tumor cells to their "normal" counterparts. Tumors with cells that least resemble normal cells are of the highest grade. Grading may be applied to any tumor in which cytologic variation occurs from tumor to tumor. Most small cell tumors are uniformly undifferentiated and, hence, do not lend themselves to grading. Most bone sarcomas may be graded. Grading is most useful in chondrosarcomas and angiosarcomas for predicting prognosis.