Double immunolabeling of central nervous system atypical teratoid/rhabdoid tumors.

The central nervous system atypical teratoid/rhabdoid tumor (ATRT) is a highly malignant tumor with a heterogeneous immunohistochemical profile and with some morphologic similarity to central nervous system primitive neuroectodermal tumors (PNET). Although several studies have investigated double immunolabeling in PNET, we are aware of no studies of double labeling of ATRT. A total of 10 ATRT from surgical and consultation materials at the Children's Hospital of Philadelphia were selected and stained for a variety of antigens using indirect immunofluorescence to detect single and double labeling. Most tumor cells showed only single labeling; rare cells showed double labeling as follows: 70% of tumors coexpressed (VIM) and glial fibrillary acidic protein (GFAP), 30% smooth muscle actin and GFAP, 20% epithelial membrane antigen (EMA) and VIM, 20% EMA/GFAP, and 20% EMA/SMA. These results are discussed in view of current debates over the histogenesis of CNS PNET and ATRT, and in reference to the classification of rhabdoid tumors as an entity or phenotype.