A patient previously reported to have Ewing's sarcoma showed a t(11;22) 
(q23;q11) and spontaneous expression of fra(11)(q23) [1]. Subsequent review of 
pathologic specimen indicated, however, that it was an Askin's tumor. Reciprocal 
translocations of chromosomes 11 and 22 are the most common cytogenetic 
abnormalities in Ewing's sarcoma and the related Askin's tumor. After radiation 
therapy of a residual metastatic brain lesion, subsequent studies of the 
recurrent brain tumor indicated the presence of the original translocations as 
well as five new reciprocal translocations and two deleted segments (9p-, 10p-). 
The new chromosome abnormalities were consistently found, indicating that 
progression of the tumor was clonal. The newly observed clonal aberrations were 
considered secondary in nature. A relationship between craniocerebral 
irradiation and development of brain tumors has been reported in several 
studies, but the mechanism for tumor induction has not yet been elucidated. It 
is important that the role of radiation therapy in the evolutionary process of 
chromosomal changes be studied in a large group of similar cases.