title: Cytomorphological features of atypical teratoid/rhabdoid tumor: an account of 12 years' experience.
abstract: Atypical teratoid rhabdoid tumor (AT/RT), an aggressive neoplasm mostly affecting young children, is characterized by rhabdoid cells together with epithelial, mesenchymal and primitive differentiation. Diagnosing AT/RT in intraoperative consultation and cerebrospinal fluid (CSF) samples may therefore pose problems. Fourteen immunohistochemically proven AT/RTs diagnosed between 2000 and 2012 were collected. Material consisted of squash smears prepared during intraoperative consultation (thirteen) and CSF smears (three). MGG-stained CSF smears and H&E stained squash smears were reviewed by a neuropathologist and a cytopathologist. The intraoperative diagnoses were based on squash preparations and 3 out of 13 were consistent with AT/RT, 4 were considered medulloblastoma/primitive neuroectodermal tumors (PNET), 3 were deferred to paraffin section for tumor typing, and another 3 were misdiagnosed as ependymoma, germinoma and malignant glioma. Morphological assessment of intraoperative squash preparations showed that AT/RTs can have a mixture of pseudopapillary and diffuse smearing patterns. Cytomorphologic features consisted of characteristic rhabdoid cells (8/9); primitive appearing cells with a high nuclear to cytoplasmic ratio (7/9); bi-/multinucleated cells (3/9); rare necrosis/apoptosis and mitoses. Three CSF smears showed high cellularity and inclusion-bearing large cells. These cells are characterized by reniform/oval, eccentrically placed nuclei with cytoplasmic perinuclear light stained areas which are not seen in intraoperative squash preparations. Differential diagnosis of AT/RT in cytology involves medulloblastoma/PNET, ependymoma, glioma and germinoma among all others. Overlapping features of AT/RT with entities in differential diagnosis are discussed with a special emphasis of rhabdoid cells being the strongest feature to aid in reaching the diagnosis of AT/RT.
authors.affiliation: Department of Pathology, Hacettepe University Faculty of Medicine, Ankara, Turkey.
authors.forename: Güneş
authors.initials: G
authors.lastname: Güner
authors.forename: Sevgen
authors.initials: S
authors.lastname: Önder
authors.forename: Figen
authors.initials: F
authors.lastname: Söylemezoğlu
mesh_terms: D001932:Brain Neoplasms / Q000175:diagnosis / Q000473:pathology*; D002555:Cerebrospinal Fluid / Q000166:cytology*; D002675:Child, Preschool; D005260:Female; D006801:Humans; D007223:Infant; D008297:Male; D018335:Rhabdoid Tumor / Q000175:diagnosis / Q000473:pathology*; D013724:Teratoma / Q000175:diagnosis / Q000473:pathology*
keywords: atypical teratoid rhabdoid tumor; brain; cerebrospinal fluid cytology; cytopathology; primitive neuroectodermal tumor; squash smear cytology