Bone Tumors

This study reports on the specific expression of the MIC2 gene, a pseudoautosomal gene located on the short arms of the X and Y chromosomes, on Ewing's sarcoma (ES) and peripheral primitive neuroectodermal tumor (pPNET) cells. The gene product, a cell membrane protein, is recognized by the newly established monoclonal antibody (MoAb) HBA-71 and the previously described MoAb 12E7 and RFB-1. Furthermore, the reaction pattern of the MIC2 antibodies, especially HBA-71, with normal tissues and a great number of benign and malignant tumors (70 different tumors, 199 tumor samples), as well as the correlation between the specific chromosomal aberrations, i.e., the t(11;22) and the del(22) and the expression of this antigen, are demonstrated. Both ES and pPNET cells express the MIC2 gene in very high amounts, which represents a highly selective and almost unique feature of these cells, making an assignment of these tumors in one entity even more likely. The MIC2 antibodies are of great value for clinical and research purposes.

Malignancies in fibrous dysplasia are rare. Most cases have been published as single case reports. The role of radiation therapy in the occurrence of sarcoma in fibrous dysplasia is still controversial. The Mayo Clinic files were reviewed, including Mayo Clinic cases and consultation cases, to collect all cases of sarcomas arising in fibrous dysplasia. Among 1122 cases with a histologic diagnosis of fibrous dysplasia, 28 cases of sarcoma were found. These 28 cases included 16 Mayo Clinic cases and 12 consultation cases. The sarcomas occurred in 19 cases of monostotic fibrous dysplasia and 9 cases of polyostotic disease (only 1 of Albright's syndrome). The most common histotype was osteosarcoma (19 cases), followed by fibrosarcoma (5 cases), chondrosarcoma (3 cases), and malignant fibrohistiocytoma (1 case). Of the 28 patients, 13 (46%) had received radiation therapy before the sarcoma developed. Most of these sarcomas occurred in the craniofacial bones (13 cases) or in the proximal femur (7 cases), followed by the humerus, pelvis, tibia, and scapula. Prognosis was poor. Sarcomas may arise with or without radiation. Early diagnosis and adequate treatment may lead to improved prognosis.