American Urological Association - Malignant Rhabdoid Tumor
Malignant Rhabdoid Tumor
- Age: generally <1 yr.; rarely over 3 years.
- Inactivation of HSNF/INI1 tumor suppressor gene located at chr 22q11.2.
- Majority presents with abdominal mass.
- Paraneoplastic hypercalcemia from production of parathyroid hormone.
- Gross: large yellow-gray or light tan friable tumor with infiltrative borders (image A).
- Large polygonal cells with abundant eosinophilic cytoplasm and large nuclei with prominent nucleoli.
- Cytoplasm typically contains large round eosinophilic inclusions that push the nucleus to the side of the cell (image B).
- Appearance simulates primitive skeletal muscle (hence the name "rhabdoid") - however this is an epithelial tumor and does NOT stain for skeletal muscle differentiation (desmin, muscle specific actin, etc.).
- Immunohistochemistry: INI1-, surrogate marker of hSNF5/INI1 gene deletion.
- Majority present with high stage tumor.
- Extremely aggressive; death from metastatic disease occurs within 12 months in 75% of patients.