CLASSIFICATION OF BONE-TUMORS

The classification of bone rumors relies on the cytologic features and products of tumor cells. This classification is reproducible and acce pted by pathologists, oncologic surgeons and oncologists. Chondrogenic tumors are the second largest group of bone tumors. Their histologic pattern suggests a relationship to hyaline cartilage. Exostoses, or os teochondromas, represent about 1/3 of chondrogenic lesions. Chondromas are hyaline cartilage tumors which can be found centrally or subperio steally; they may contain some calcifications and/or ossifications. Ch ondroblastomas are tumors whose cells produce, at least focally, a mat rix similar to hyaline cartilage. Histology of chondromyxoid fibromas shows large or small areas where proliferating cells produce a matrix resembling the hyaline cartilage. Chondosarcomas are tumors whose mali gnant cells produce a cartilaginous matrix. Most of them occur in prev iously normal bones: they are classified as conventional or primary ch ondrosarcomas. Secondary chondrosarcomas result from the malignant tra nsformation of a benign cartilaginous lesion-less commonly enchondroma s and most commonly osteocartilaginous exostoses, or osteochondromas. Less common variants include dedifferentiated, mesenchymal and clear c ell chondrosarcomas. Osteogenic tumors are the third largest group of bone tumors, with osteosarcomas being the most frequent type. The most important criterion for a tumor to be considered an osteosarcoma is t hat the malignant tumor cells must produce a recognizable osteoid matr ix, at least focally. Osteosarcomas are divided into three groups: ost eoblastic, chondroblastic and fibroblastic, according to the dominant histologic feature. Osteosarcomas can be multifocal, synchronous or me tachronous; they are also classified by the histologic grade of malign ancy. Pathologically low grade lesions, which are clinically indolent, are generally known as low grade central and parosteal osteosarcomas. (C) 1998 Elsevier Science Ireland Ltd. All rights reserved.