Pleuropulmonary blastoma: fluorescence in situ hybridization analysis indicating trisomy 2

We report a case of pleuropulmonary blastoma occurring in the right upper lobe and pleura of a 29-month-old boy. Histologically, the tumor was composed of undifferentiated mesenchymal cells with occasional rhabdomyoblastic and chondroid differentiation. Immunohistochemical analysis showed vimentin immunoreactivity in most of the tumor cells, myoglobin, desmin, and actin in the rhabdoid cells, and S-100 protein in the chondroid cells. Fluorescence in situ hybridization (FISH) analysis showed trisomy 2 and normal chromosomal copy numbers for chromosomes 7, 12, 17, 18, and X in the majority of the tumor cell nuclei. The identification of trisomy 2 in the current pleuropulmonary blastoma confirms a previous cytogenetic finding of chromosome 2 abnormality with cultured metaphase cells of a similar case, indicating that the acquisition 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 have an intimate tumorigenetic relationship with embryonal rhabdomyosarcoma.