Malignant rhabdoid tumor

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]Associate Editor(s)-in-Chief: Sujit Routray, M.D. [2]

Synonyms and keywords: Malignant rhabdoid tumour; Malignant rhabdoid neoplasm; Atypical teratoid rhabdoid tumor

Overview

• Malignant rhabdoid tumor is one of the aggressive tumors in the pediatric population. It was originally described as a rhabdomyosarcomatoid variant of Wilms' tumor, which is primarily a renal tumor.
• Malignant rhabdoid tumor was first described as a variant of Wilms' tumor of the kidney, in 1978.
• Malignant rhabdoid tumor is classified into two groups: renal and extrarenal.
• Malignant rhabdoid tumor is comprised of rhabdoid tumor cells and varying amounts of small undifferentiated primitive neuroectodermal tumor (PNET)-like, mesenchymally, and/or epithelially differentiated tumor cells.
• Gene involved in the pathogenesis of malignant rhabdoid tumor include SMARCB1 (hSNF5/INI-1), a tumor suppressor gene.
• Malignant 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 maintenance of the mitotic spindle and cell cycle control.
• Malignant rhabdoid tumor may be associated with rhabdoid predisposition syndrome.
• Common locations associated with malignant rhabdoid tumor include:

• Kidney: malignant rhabdoid tumor of the kidney (most common)
• Intracranial: atypical teratoid rhabdoid tumor
• Soft tissues: breast, skin, orbit, liver, etc

• On gross pathology, malignant rhabdoid tumor of the kidney is characterized by large, centrally located, heterogeneous soft-tissue masses involving the renal hilum with indistinct margins.
• On microscopic histopathological analysis, malignant 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.
• Almost all reported cases of malignant rhabdoid tumor, regardless of site of origin, occur in young children between birth and 2 years of age.
• In approximately 10% of cases of renal malignant rhabdoid tumor, the patients subsequently develop intracranial atypical teratoid rhabdoid tumor.
• Common complication of malignant rhabdoid tumor include hypercalcemia, secondary to elevated parathyroid hormone levels.
• Prognosis is generally poor, with a reported mortality rate of patients with malignant rhabdoid tumor is 80 to 100%.
• Symptoms of malignant rhabdoid tumor of kidney include:

• Blood in urine
• Flank mass

• CT scan may be diagnostic of malignant rhabdoid tumor. Findings on CT scan suggestive of malignant rhabdoid tumor include a large, heterogenous, centrally located mass, which is lobulated with individual lobules separated by intervening areas of decreased attenuation, relating to either previous hemorrhage or necrosis. Enhancement is similarly heterogeneous. Calcification is relatively common, observed in 20-50% of cases and is typically linear and tends to outline tumur lobules.