Atypical teratoid rhabdoid tumor pathophysiology

Atypical teratoid rhabdoid tumor is comprised of rhabdoid tumor cells and varying amounts of small undifferentiated primitive neuroectodermal tumor (PNET)-like mesenchymal, and/or epithelial differentiated tumor cells. Gene involved in the pathogenesis of atypical teratoid rhabdoid tumor include SMARCB1 (hSNF5/INI-1), a tumor suppressor gene. Atypical teratoid rhabdoid tumor may be associated with rhabdoid predisposition syndrome. On gross pathology, atypical teratoid rhabdoid tumor is characterized by an encapsulated, grayish, friable mass which is moderately vascular. On microscopic histopathological analysis, atypical teratoid rhabdoid tumor is characterized by round blue tumor cells of high cellularity composed of atypical cells with eccentric nuclei, small nucleoli, and abundant amounts of eosinophilic cytoplasm with frequent mitotic figures. Atypical teratoid rhabdoid tumor is demonstrated by positivity to tumor markers such as epithelial membrane antigen, vimentin, and smooth muscle actin.

• Atypical teratoid rhabdoid tumor is comprised of rhabdoid tumor cells and varying amounts of small undifferentiated primitive neuroectodermal tumor (PNET)-like mesenchymal, and/or epithelial differentiated tumor cells.^[1]

• Gene involved in the pathogenesis of atypical teratoid rhabdoid tumor include SMARCB1 (hSNF5/INI-1), a tumor suppressor gene.^[2]
• Atypical teratoid rhabdoid tumor is characterized by loss of the long arm of chromosome 22, which results in loss of the hSNF5/INI-1 gene.
• INI1, a member of the SWI/SNF chromatin remodeling complex, is important in the maintenance of the mitotic spindle and cell cycle control.

• Atypical teratoid rhabdoid tumor may be associated with rhabdoid predisposition syndrome.^[1]

• On gross pathology, atypical teratoid rhabdoid tumor is characterized by an encapsulated, grayish, friable mass which is moderately vascular.^[3]
• Common intracranial sites associated with atypical teratoid rhabdoid tumor include:^[4]

• On microscopic histopathological analysis, atypical teratoid rhabdoid tumor is characterized by the round blue tumor cells of high cellularity composed of atypical cells with eccentric nuclei, small nucleoli, and abundant amounts of eosinophilic cytoplasm with frequent mitotic figures.^[1]
• According to the WHO classification of tumors of the central nervous system, atypical teratoid rhabdoid tumor is classified into a WHO grade IV tumor.

• Atypical teratoid rhabdoid tumor is demonstrated by positivity to tumor markers, such as:^[5][6]

• Epithelial membrane antigen
• Vimentin
• Smooth muscle actin
• GFAP
• Cytokeratin
• Neurofilament
• Desmin

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