p53 GENE MUTATIONS IN PLEUROPULMONARY BLASTOMAS

Pleuropulmonary blastoma (PPB) is rare childhood tumor oniginating from either lung or pleura. Although several cytogenetic changes, such as tisomy 2, trisomy 8, and loss of 17p material, have been reported, evidence of gene mutations is still lacking. Pathologically, PPB shares similarities with rhabdomyosarcoma in which p53 mutations arefrequently detected. Possible implication of p53 mutations in PPB was investigated. PPBs of 3 patients were analyzed for occurrence of p53 mutations by using polymerase chain reaction-single-strand conformation polymorphism (PCR-SSCP) method, and the nature of mutations was confirmed by direct sequencing. Two PPBs were confirmed to harbor p53 mutations. One was a Val to Leu substitution at codon 173, and another was a ArgArg to TrpCys substitution at codons 282 and 283. In each tumor, only the mutated allele was detected, suggesting inactivation of p53. Both patients with mutations had fatal outcome, while the remaining patient in whom no mutation was detected is disease free for 3 years after completion of treatment. The results raise the possibility that p53 inactivation can occur as a nonrandom genetic change involving the pathogenesis and outcome of PPB. Further studies in a larger series are necessary to clarify these matters.