A case of Ewing's sarcoma of the bone, arising in the right radius of a 12-year-old girl, which showed unique histologic features after pre-operative treatment, is reported. The light microscopic features of a biopsy sample were those of a small round cell tumor showing positive immunoreaction with antibodies against the product of the MIC 2 gene (O13), neuron-specific enolase, neurofilament, and synaptophysin, but no morphological differentiation. The patient received combined intensive multi-drug chemotherapy and radiation before surgery. Examination of the surgical specimen showed that the tumor was less cellular than that in the biopsy specimen, and was composed mainly of loosely textured large cells mimicking ganglion cells, occasionally forming Homer-Wright rosettes. An immunohistochemical study revealed that neural differentiation was enhanced. Immunoreactivity for Leu-7 also became positive. Although the patient underwent postoperative chemotherapy, she died of multiple lung and bone metastases 30 months after the diagnosis. Autopsy showed that metastatic foci were made up of densely packed small round cells like those seen in the biopsy samples, but associated with prominent Homer-Wright rosettes. To the authors' knowledge, this is the first report of a tumor being replaced almost entirely by ganglion cells after pre-operative chemotherapy and radiotherapy.

W e present two cases of osteochondroma after total body irradiation in bone marrow recipients, the first in a 6-year-old boy with juvenile chronic myelogenous leukemia and the second in a 13-year-old boy with acute myelogenous leukemia. The patients developed multiple osteochondromas three years and seven years, respectively, after 12 Gy of total body irradiation. Neither had a family history of hereditary multiple osteochondromatosis. A review of the English literature revealed only one report describing five cases of osteochondroma after 12 Gy of total body irradiation in bone marrow transplant recipients. Osteochondroma should be considered as an additional adverse effect of total body irradiation. (Jpn J Clin Oncol 26: 480-483, 1996)

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