Histological investigation for comparison of cartilaginous tumors of unknown biological course with unequivocal chondrosarcomas.

Morphological findings recorded from chondromatous tumors of unknown biological behaviour (n = 40) were compared with those obtained from unequivocal chondrosarcomas (n = 27), and the histological results were evaluated by clinical outcome. The morphological details were analysed by histological set up and summarized by Mirra et al. (1985): Two benign patterns, the enchondroma encasement pattern and the island of cartilage patterns, were the most common findings in cartilaginous tumors of unknown biological behaviour. Malignant patterns, such as chondrosarcoma permeation, invasion of the Haversian system, soft tissue mass and bands of fibrosis patterns were detected only in unequivocal chondrosarcomas. However, the enchondroma encasement pattern could be focally demonstrated also in central chondrosarcomas (n = 3), a phenomenon, which in our opinion could not be interpreted as being indicative of a preexisting benign lesion. Morphological classification of chondromatous tumors of unknown biological behaviour, as a group of benign cartilaginous tumors, enables their discrimination from unequivocal chondrosarcomas. This was also confirmed by the significant difference (p = 0.0065; Mantel-Cox) among survival curves after Kaplan and Meier (1958). We conclude that the above criteria, when applied with due caution, are helpful in classifying chondromatous tumors.