Congenital mesoblastic nephroma: cytogenetic comparison to leiomyoma

We report the karyotype analysis of a congenital mesoblastic nephroma (CMN), a usually benign renal tumor occurring most commonly during early infancy. The tumor was composed of interlacing bundles of spindle-shaped cells and it displayed both the classic and cellular histologic patterns. Immunoperoxidase studies showed reactivity for vimentin and actin. The tumor cell karyotype included additional chromosomes 11 and an altered chromosome 12. Trisomy or tetrasomy of chromosome 11 is present in five of six reported cases and may represent a frequent alteration in the karyotype of the CMN. Furthermore, breakpoints in the q13-15 region of chromosome 12 are commonly seen in leiomyomas, which are histologically similar to the CMN. Thus, the karyotype described here illustrates another similarity between the two tumor types.