PLEUROPULMONARY BLASTOMA - FLUORESCENCE IN-SITU HYBRIDIZATION ANALYSIS INDICATING TRISOMY-2

We report a case of pleuropulmonary blastoma occurring in the right up per lobe and pleura of a 29-month-old boy. Histologically, the tumor w as composed of undifferentiated mesenchymal cells with occasional rhab domyoblastic and chondroid differentiation. Immunohistochemical analys is showed vimentin immunoreactivity in most of the tumor cells, myoglo bin, desmin, and actin in the rhabdoid cells, and S-100 protein in the chondroid cells. Fluorescence in situ hybridization (FISH) analysis s howed trisomy 2 and normal chromosomal copy numbers for chromosomes 7, 12, 17, 18, and X in the majority of the tumor cell nuclei. The ident ification of trisomy 2 in the current pleuropulmonary blastoma confirm s a previous cytogenetic finding of chromosome 2 abnormality with cult ured metaphase cells of a similar case, indicating that the acquisitio n of an additional chromosome 2 copy in pleuropulmonary blastoma is a nonrandom chromosomal alteration and that pleuropulmonary blastoma is cytogenetically distinct from pulmonary blastoma in which chromosome 2 is bisomic. It is also suggested that pleuropulmonary blastoma may ha ve an intimate tumorigenetic relationship with embryonal rhabdomyosarc oma.