CSF cytology of atypical teratoid/rhabdoid tumor of the brain in a two-year-old girl: a case report.

Atypical teratoma/rhabdoid tumor (AT/RT) of the central nervous system is a highly malignant neoplasm in infants and early childhood. Approximately one third of patients develop intracranial dissemination with involvement of cerebral spinal fluid (CSF). The clinical, radiological, and pathological features have been described, but cytology of the tumor cells in CSF has not. Multiple CSF samples were examined in a case of AT/RT in a 2-yr-old girl. The most consistent cytologic features of AT/RT are the large size of the tumor cells, eccentricity of the nuclei, and prominent nucleoli. The differential diagnosis includes medulloblastoma/primitive neuroectodermal tumor (PNET) of the brain. Because AT/RT often contains PNET-like regions, the differential diagnosis mainly relies on the presence or absence of large rhabdoid tumor cells. Cytological examination of CSF from a patient with AT/RT is important in the early diagnosis, disease progression analysis, and therapy modulation.