To the Editor:— Even with histologic study it may be difficult to distinguish benign chondromas from chondrosarcomas. Benign chondromas are about as cellular as normal cartilage and composed for the the most part of uniform cells with single nuclei in individual lacunae. At the other extreme are the cellular chondrosarcomas with pleomorphic and often multinucleated tumor cells. In between the extremes is a nearly complete spectrum of lesions of varying cellularity. In actual practice it is often difficult to distinguish between benign and malignant tumors of cartilage since there is more of a continuous spectrum of these tumors than with some other kinds of neoplasms. Benign chondromas occur most commonly in the extremities. It is unusual to have a benign chondroma of the ribs or pelvic bones. Yet these are the sites where chondrosarcoma is most frequent. In classifying these tumors, anatomic site is important. In general, histologically identical lesions