Surgical Pathology Criteria

Extrarenal Rhabdoid Tumor

Differential Diagnosis

Carcinomas may mimic extrarenal rhabdoid tumors and in rare cases be morphologically indistinguishable

Melanomas may mimic extrarenal rhabdoid tumors and in rare cases be morphologically indistinguishable

Anaplastic Large Cell Lymphoma Extrarenal Rhabdoid Tumor
LCA and or T lineage markers positive LCA and T lineage markers negative
Keratin rare, faint Keratin 100% positive
CD30, ALK positive No data available for CD30, ALK
INI1 expressed 100% (few tested) INI1 loss 85%
Translocation of chromosome 2 short arm Various deletions, translocations involving 22q11
LCA and T lineage markers are occasionally undetectable in ALCL

Extrarenal Rhabdoid Tumor Proximal Type Epithelioid Sarcoma
CD34 negative CD34 50% positive
No intensely eosinophilic collagen Intensely eosinophilic collagen
Median age 8-9 years Median age 35-40 years
Wide range of sites Predilection for genitalia
It is probable that malignant rhabdoid tumors do not occur in adults - most if not all are carcinoma, melanoma or proximal epithelioid sarcoma

Rhabdomyosarcoma Extrarenal Rhabdoid Tumor
Desmin, actin, myoglobin or MyoD1 positive Muscle markers negative (definitional)
Keratin 5-50% positive, focal, weak Keratin 100% (definitional)
INI1 expression retained 100% INI1 loss 85% nearly definitional
May have cross striations No cross striations
May have strap cells Strap cells rare
No consistent abnormalities of 22q Various deletions, translocations involving 22q11 may be seen
Both have eccentrically located eosinophilic cytoplasm

Extrarenal Rhabdoid Tumor Desmoplastic Small Cell Tumor
No desmoplastic stroma Prominent desmoplastic stroma
Desmin negative Desmin positive
INI1 loss 85% INI1 expressed 100%
Median age 8-9 years Mean age 25 years
Various deletions, translocations involving 22q11 t(11;22)(p13;q12)
Both may be rhabdoid and express keratin

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