Surgical Pathology Criteria

Peripheral Primitive Neuroectodermal Tumor

Differential Diagnosis

Neuroblastoma Peripheral Primitive Neuroectodermal Tumor
CD99 negative CD99 positive
Dense chromatin Fine chromatin
Serum catecholamines elevated Normal catecholamines

 

Rhabdomyosarcoma Peripheral Primitive Neuroectodermal Tumor
Usually irregular nuclei Usually uniform nuclei
Usually dense chromatin Usually fine chromatin
Variable amounts of cytoplasm Usually scant cytoplasm
No rosettes May have rosettes
CD99 rare to 50% CD99 >90%
Muscle markers positive Muscle markers only in ectomesenchymoma variant
Translocations t(2;13) or t(1:13) in alveolar rhabdomyosarcoma Translocations involving 22q12

 

Lymphoma Peripheral Primitive Neuroectodermal Tumor
LCA or lineage markers positive LCA, B and T markers negative
CD99 may be positive in >50% of T leukemias and T lymphoblastic lymphomas

 

The small cell pattern of DSCT may be confused with PPNET
Peripheral Primitive Neuroectodermal Tumor Desmoplastic Small Cell Tumor
CD99 positive CD99 35%
WT1 negative WT1 positive
Desmin only in ectomesenchymoma variant Desmin positive
Keratin 5-15% Keratin positive
EMA negative EMA positive
No desmoplastic stroma Prominent desmoplastic stroma
Various translocations involving 22q12 (no translocations involving 11p13) t(11;22)(p13;q12)

 

Esthesioneuroblastoma Peripheral Primitive Neuroectodermal Tumor
CD99 negative CD99 >90%
S100+ sustentacular cells in 75% of cases No sustentacular cells

 

Small Cell Osteosarcoma Peripheral Primitive Neuroectodermal Tumor
CD99 negative to rare CD99 >90%
Malignant osteoid present at least focally No osteoid

 

Mesenchymal Chondrosarcoma Peripheral Primitive Neuroectodermal Tumor
Islands of hyaline cartilage Hyaline cartilage rare
Cartilaginous areas S100 positive S100 negative
No translocations involving 22q12 Various translocations involving 22q12
Mesenchymal chondrosarcoma may be CD99 positive

 

Nephroblastoma Peripheral Primitive Neuroectodermal Tumor
CD99 rare to 50% CD99 >90%
Kidney primary Wide variety of sites
No translocations involving 22q12 Various translocations involving 22q12

 

Oat Cell Carcinoma Peripheral Primitive Neuroectodermal Tumor
CD99 <10% positive CD99 >90%
Age usually >50 years Age nearly always <40 years
Keratin positive Keratin rare
Very scant cytoplasm Cytoplasm clearly discernable
Nuclear molding No nuclear molding
No translocations involving 22q12 Various translocations involving 22q12

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