Nuclear morphometry as a prognostic indicator for genitourinary rhabdomyosarcoma: a preliminary investigation. Rhabdomyosarcoma of the urogenital tract is a malignant mesenchymal tumor seen primarily in childhood. Multimodal therapy, encompassing surgery, radiotherapy and chemotherapy, has dramatically improved the survival of patients with this disease. However, the quest for markers of tumor aggression is important to decrease the morbidity of treatment given to patients with good prognosis tumors, while at the same time intensifying treatment of tumors with poor prognosis. Using archival tumor specimens from 13 patients with genitourinary rhabdomyosarcoma, a multivariate analysis of multiple nuclear shape descriptors was done with the Hopkins Morphometry System. Three nuclear shape descriptors clearly separated patients with no evidence of disease recurrence or progression from those with recurrent disease, progressive disease or death of disease. These nuclear shape descriptors were standard error of the chain code standard deviation analysis (p = 0.010), range of the feret ellipticity distribution (p = 0.016) and standard error of the chain code range analysis (p = 0.037). With multivariate analysis these shape descriptors taken together separated patients with good and poor prognoses to a level of significance of p = 0.007. Thus, nuclear morphometric analysis may prove to be useful as an individual prognostic indicator in childhood genitourinary rhabdomyosarcoma and warrants further analysis in a much larger, blinded, controlled study. 