Table of Contents
Washington University Experience | NEOPLASMS (EMBRYONAL) | ATRT - Atypical Teratoid Rhabdoid Tumor | 1K ATRT (Case 1) Ki67 2.jpg
The proliferative index in this case is very high (~90%). (Ki67 IHC) ---- Denouement: Even though this tumor lacks the classic 'rhabdoid cells' of AT/RT and has a primitive neuroectodermal tumor (PNET)-like appearance on H&E evaluation, its loss of INI-1 expression is consistent with a diagnosis of AT/RT. Since these tumors often harbor divergent differentiation, additional ancillary work-up was performed and it showed reactivity for vimentin, smooth muscle actin, and epithelial membrane antigen; the tumor is essentially non-reactive for desmin. These findings support its polyphenotypic immunoprofile. The overall findings are consistent with an atypical teratoid/rhabdoid tumor (AT/RT), WHO grade IV. Per imaging, it is multifocal with evidence of leptomeningeal dissemination.
