Pathology Cheat Sheet
Site Plus Morphology
Childhood tumours for NEET-PG exams: neuroblastoma MYCN, stage 4S regression, Wilms tumour WT1, retinoblastoma two-hit, and Ewing sarcoma EWS-FLI1 fusion.
MedNext Academy | 3 min read
Site Plus Morphology
Childhood tumours for NEET-PG exams: neuroblastoma MYCN, stage 4S regression, Wilms tumour WT1, retinoblastoma two-hit, and Ewing sarcoma EWS-FLI1 fusion.
The tumours and tumour-like conditions of infancy and childhood, focusing on small round blue cell tumours and their site and marker clues.
High-yield lines
- Paediatric tumours often arise from primitive embryonal cells and appear as small round blue cell tumours with a high nuclear-to-cytoplasmic ratio.
- Neuroblastoma is the most common extracranial solid tumour of childhood and the most common tumour of infancy.
- About half of neuroblastomas arise in the adrenal medulla and the rest along the sympathetic chain.
- Neuroblastoma shows Homer-Wright rosettes and secretes catecholamine metabolites, raising urinary VMA and HVA.
- MYCN amplification in neuroblastoma defines high-risk disease and a poor prognosis.
- Stage 4S neuroblastoma in infants can undergo spontaneous regression or maturation to ganglioneuroma.
- Wilms tumour (nephroblastoma) is the most common renal tumour of childhood and shows a triphasic pattern of blastema, epithelium, and stroma.
- Wilms tumour is associated with WT1 mutation and syndromes such as WAGR and Beckwith-Wiedemann.
- Retinoblastoma is the classic two-hit tumour and shows Flexner-Wintersteiner rosettes.
- Ewing sarcoma is a small round blue cell tumour of bone driven by the EWS-FLI1 fusion from t(11;22).
- Rhabdomyosarcoma is the most common soft tissue sarcoma of childhood and expresses desmin and myogenin.
- Correlating tumour site with immunohistochemical markers is essential to classify small round blue cell tumours.
Mapped competency codes
- PA11.2
Continue into the full chapter
This summary maps to PA11-genetic-and-paediatric-diseases.
Frequently Asked Questions
What is the most common extracranial solid tumour of childhood?
Neuroblastoma, a tumour of primitive sympathetic neuroblasts that most often arises in the adrenal medulla or along the sympathetic chain.
Which molecular marker indicates high-risk neuroblastoma?
MYCN amplification, which defines high-risk disease, prevents differentiation, and confers a poor prognosis.
What is the characteristic histology of Wilms tumour?
A triphasic pattern of blastema, epithelial tubules, and stroma, associated with WT1 mutation and syndromes such as WAGR and Beckwith-Wiedemann.
Which translocation drives Ewing sarcoma?
The t(11;22) translocation creating the EWS-FLI1 fusion gene, seen in this small round blue cell tumour of bone.
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