CYTOGENETIC FINDINGS IN A CASE OF CONGENITAL MESOBLASTIC NEPHROMA

Congenital mesoblastic nephroma (CMN) is a benign, but locally agressi ve, renal tumor of early infancy. Few metastases have been reported, b ut local recurrence is well documented. CMN is histologically distinct from Wilms' tumor and other childhood renal tumors, and is typically treated by surgical excision without adjuvant therapy. Cytogenetic abn ormalities in these tumors have been described and ore often compared with abnormalities seen in leiomyomas, fibromatoses, and infantile fib rosarcomas. In particular, trisomy 11 has been suggested as a nonrando m occurrence in CMNs. We describe a case of CMN in a 4-month-old femal e infant. The diagnostic histologic features included a monophasic mes enchymal appearance, prominent staghorn vascular spaces, and extensive infiltration of the adjacent kidney. Cytogenetic analysis showed a hy perdiploid chromosome number and a single structural abnormality invol ving a translocation between chromosomes 12 and 15. The composite kary otypic interpretation was: 46-47XX, - X, + 8, + 11,t(12;15) (p12;q25), + 17, + 20(cp14). The significance of karyotypic changes in this tumo r is currently unknown. A generic basis for histologic variability and progression may exist if certain cytogenetic abnormalities, such as t risomy 11 or specific translocations, confer a proliferative advantage . Additional cases are required to correlate cytogenetic findings with the biologic behaviors of CMN. We present this case as a contribution to existing literature describing these relatively rare and interesti ng renal tumors.