We report on a 7-year-old boy with mosaic variegated aneuploidy (MVA) who developed embryonal rhabdomyosarcoma of the soft palate. This patient is the 11th case report of MVA and represents further documentation of the true existence of this rare mitotic mutant. Clinical findings share similarities to those previously described patients including microcephaly and growth retardation as the two most common abnormalities. Notably, mental retardation is not universally present. Results of serial cytogenetic analyses performed on somatic and neoplastic tissues are reviewed and compared with those of other previously reported patients. We postulate that mosaic variegated aneuploidy is causally related to the development of rhabdomyosarcoma in our patient. This is the first report of a patient with MVA who developed cancer and suggests that these patients may be at risk for malignancy and require long-term follow-up and cancer surveillance.