Primitive neuroectodermal tumor (PNET) is a highly malignant tumor composed of small round cells of neuroectodermal origin that affects soft tissue and bone. PNETs are classified into groups depending on location, with peripheral PNET (pPNET) occurring in soft tissue and bone outside the central nervous system. pPNET includes Ewing sarcoma and Askin tumor. Diagnosis involves ruling out other small round cell tumors through molecular cytogenetic studies showing translocation between chromosomes 11 and 22. PNET most commonly presents in adolescents and young adults with pain, swelling, and mass effect. Prognosis depends on tumor site, volume, and presence of metastasis. Treatment involves complete surgical resection when possible along with

1. PRIMITIVE NEUROECTODERMAL
TUMOR
DR RUPESH
BASE HOSPITAL DELHI CANTT

2. DEFINATION
• A group of highly malignant tumors composed
of small round cells of neuroectodermal origin
that affects soft tissue and bone.

3. CLASSIFICATION
• Batsakis(1996)
• 3 groups
A- CNS PNET
B- Neuroblastoma
C- Peripheral PNET

4. pPNET
• Ewing sarcoma (osseus and extraosseus)
• Malignant Ppnet or peripheral
neuroepithelioma of bone and soft tissues
• Askin tumor(peripheral neuroepithelioma of
thoracopulmonary region)
• Other less common tms- neuroectodermal tm,
ectomesenchymoma, peripheral
medulloepithelioma.

5. D/D of small round cell tm
• Rhabdomyosarcoma
• Lymphoma
• Neuroblastoma
• Nephroblastoma
• Medulloblastoma
• retinoblatoma
• PNET/Ewing sarcoma

6. Difference from other round cell tm
• Molecular cytogenetic studies
• Reciprocal translocation between
chromosome 11 and 22

7. Epidemiology
• Under reported due to recent diagnostic
techniques
• Age group- Birth to 20 years
• 2.9 per million
• Slight male predominence
• 4-17% of all paediatric soft tissue tm

8. C/F
• Most pNET manifest in thoracopulmonary
region(Askin tm), pelvis, abdomen and
extremities
• Presentation is diverse depending on site of
involvement but invariably include pain and
swelling of surrounding structures due to mass
effect.
• Individual cranial neuropathy, exophalmos,
epistaxis, nasal obstruction, anosmia, neck
masses and headache.

9. Prognostic factors
• Site – Paraspinal/scapular disease>head and
neck pNET > abdominopelvic disease
• Tumor volume
• Presence of metastasis- lung, bone, BM

10. Pathological features
• Microscopy
• Cytogenetic analysis
• Immunohistochemistry

11. Microscopy
• Monotonous collection of small,round and
darkly stained cells
• pPNET under electron microscopy reveals
neurosecretory granules with microtubules
and microfilaments. In addition short
dendritic processes lie between cells in pPNET
in contrast to Ewing sarcoma in which
dendritic processes are absent.

13. Cytogenetics
• In 85% cases, translocation involving EWS
gene (22q12) and FLI-1 (11q24)
• 5-10% case, EWS And ERG(21q22)

14. IMMUNOHISTOCHEMISTRY
• Used to detect antibobies to FLI-1 in gene
fusion product of EWS.
• MIC-2 gene produces MIC-2 antigen which
consistently identifies pPNET and Ewing
sarcoma.
• pPNET typically coexpresses CD99
(glycoprotein MIC2) and vimentin.
• Non specific markers- S-100,Non-specific
enolase, CD75 and synaptophysin.

15. Work up
• Tissue biopsy with cytogenetic and
immunohistochemistry studies
• CT scan and MRI to study extent of lesion

16. treatment
• Complete surgical resection with negative
margins whenever possible adjuvant and
neoadjuvant CT and RT.
• Vincistine,doxorubicin and cyclophosphamide
with ifosfamide and etoposide
• RT- risk of sarcoma, AML, Hypothyroidism
(>60 Gy)
• <48 Gy – no risk of secondary malignancies

17. THANK YOU