Congenital disseminated malignant rhabdoid tumor - A distinct clinicopathologic entity demonstrating abnormalities of chromosome 22q11

The clinical, pathologic, and immunohistochemical features of a widely diss eminated tumor with rhabdoid phenotype are described in nine infants less t han or equal to 3 months of age. Five neonates had tumor evident at birth, two of which had placental metastases. The average survival following diagn osis was < 6 weeks. None of the infants had an apparent primary tumor in ei ther the kidney or brain. In four cases, the dominant mass involved the hea d and neck region, and in two cases, the primary mass was paraspinal. The h istologic features were those of a high-grade, round cell neoplasm with abu ndant cytoplasm and containing cells with cytoplasmic filamentous inclusion s. Immunohistochemical studies revealed polyphenotypic antigen expression. Genetic information was available from eight of nine cases. Karyotype analy sis revealed abnormalities of chromosome band 22q11-12 in three of six tumo rs. Fluorescence in situ hybridization studies or molecular studies demonst rated 22q11.2 deletions in all five cases with available frozen tissue, two of which had translocations involving 22q by karyotype analysis. The simil ar clinical and pathologic findings in these rapidly fatal tumors in infant s and the demonstration of abnormalities of chromosome 22q11 in a majority of the cases supports their histogenetic and nosologic relationship to the family of malignant rhabdoid tumors that typically occur in young children in several anatomic sites, including kidney, soft tissues, liver, and brain . Like neuroblastoma and rhabdomyosarcoma, malignant rhabdoid tumor can app ear as disseminated disease at birth or shortly thereafter.