Ring chromosome in parosteal osteosarcoma. Clinical and diagnostic significance.

In this study, two specimens of a parosteal osteosarcoma, a rare primary bone neoplasm comprising only 3-6% of all osteosarcomas, were cytogenetically analyzed utilizing standard techniques. In contrast to the complex karyotypes previously reported in osteosarcoma, this particular histologic subtype was characterized by a single chromosomal aberration, a ring chromosome. Ring chromosomes have been described as characteristic for two other low-grade malignant mesenchymal neoplasms, well-differentiated liposarcoma and dermatofibrosarcoma protuberans. We propose that the observation of a ring chromosome in osteosarcoma also correlates with a low-grade malignant potential.