Central nervous system atypical teratoid/rhabdoid tumors of infancy and childhood: definition of an entity

TLDR

ATT/RhTs are frequently misdiagnosed as PNETs because 70 % contain indistinguishable fields, they are most common in infants under 2 years, and clinical signs and imaging cannot differentiate them. The study aims to distinguish ATT/RhTs from PNETs because ATT/RhTs have a poor prognosis despite surgery and adjuvant therapy. In 52 cases, ATT/RhTs were intracranial in all but one, one‑third had subarachnoid spread at presentation, were composed of rhabdoid cells (13 % entirely, 77 % partly), contained typical PNET fields in 70 %, displayed a unique immunoprofile (EMA, vimentin, SMA positive, germ‑cell markers negative), and were distinguished from PNETs by chromosome 22 abnormalities versus i(17q) in PNETs.

Abstract

✓ Clinical and pathological features of 52 infants and children with atypical teratoid/rhabdoid tumor (ATT/RhT) of the central nervous system are defined. This tumor is typically misdiagnosed as a primitive neuroectodermal tumor (PNET) primarily because 70% of ATT/RhTs contain fields indistinguishable from classic PNETs. Separation of these two tumor types is crucial because the prognosis for ATT/RhT is grim even when treatment includes surgery with or without radio- and/or chemotherapy. These tumors are most common in infants less than 2 years of age. The cases described in this study arose intracranially in all but one instance, although one-third had already spread throughout the subarachnoid space at presentation. Clinical signs and symptoms and radiological features do not distinguish ATT/RhTs from PNETs. The tumors are composed entirely (13%) or partly (77%) of rhabdoid cells. Seventy percent contain fields of typical PNET alone or in combination with mesenchymal and/or epithelial elements. The immunohistochemical profile is unique: epithelial membrane antigen, vimentin, and smooth-muscle actin are positive in the majority of tumors and markers for germ-cell tumors are consistently negative. Abnormalities of chromosome 22 distinguish ATT/RhTs from PNETs, which typically display an i(17q) abnormality.