Paediatric Tumours
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Direct answer
Behind the leukaemias and CNS tumours that lead childhood cancer statistics, the solid lesions cluster into the "small round blue cell" family — neuroblastoma, Wilms tumour, Ewing sarcoma, rhabdomyosarcoma and retinoblastoma — where a bare haematoxylin-eosin slide is rarely enough and diagnosis combines morphology, immunohistochemistry, cytogenetics and clinical syndromes. Age predicts the tumour: neuroblastoma and teratomas dominate infancy, Wilms peaks at three to four years, Ewing and osteosarcoma arrive in the second decade. Indian practice adds a sobering constant — retinoblastoma and other childhood solid tumours commonly present late, advanced and sometimes only after months of symptomatic treatment, so staging at diagnosis drives everything.
What you must remember
- Neuroblastoma: most common extracranial solid tumour of childhood; adrenal medulla origin, Homer-Wright pseudorosettes, urinary VMA and HVA, N-myc amplification predicts poor outcome, and stage 4S in infants can regress spontaneously.
- Wilms tumour: most common renal malignancy of childhood, peak three to four years, triphasic pattern of blastema, epithelium and stroma; anaplasia (not stage alone) defines unfavourable histology; associations include WAGR, Denys-Drash and Beckwith-Wiedemann.
- Hepatoblastoma: most common paediatric liver tumour, under three years, serum AFP markedly raised, associated with prematurity and low birth weight.
- Retinoblastoma: most common intraocular malignancy of childhood; RB1 at 13q14, Knudson two-hit; Flexner-Wintersteiner rosettes and calcification; India carries a large share of global cases with frequent extraocular disease at presentation.
- Rhabdomyosarcoma: embryonal type (including botryoid sarcoma of genitourinary sites) in infants, alveolar type in adolescents with PAX3/PAX7-FOXO1 fusion and worse outlook; myogenin and desmin positive.
- Ewing sarcoma: diaphyseal, t(11;22) EWS-FLI1 fusion, CD99 membranous positivity, onion-skin periosteal reaction.
- Two quick claims: sacrococcygeal teratoma is the most common tumour of newborns; Langerhans cell histiocytosis shows Birbeck granules (tennis-racket organelles) with CD1a and S100 positivity.
An abdominal mass sorted by age
A three-year-old with a painless left abdominal mass crossing the midline, hypertension and a calcified suprarenal lesion on ultrasound points to neuroblastoma; the same mass confined to the kidney, smooth and with a "claw" of renal tissue, in a child of similar age points to Wilms. The pathway then diverges on biochemistry and histology — urinary catecholamines and marrow with tumour rosettes confirm neuroblastoma, whereas a triphasic tumour with blastemal islands confirms Wilms. Move the clock forward: a 14-year-old with a painful femoral diaphyseal lesion, fever and onion-skin periosteal reaction is Ewing sarcoma until a CD99-positive, MIC2-staining small round cell tumour with t(11;22) says otherwise. Age plus site plus radiographic character narrows this family faster than any single immunostain, which is why exam vignettes always supply all three.
Where students slip
Rosette confusion costs the most marks: Homer-Wright pseudorosettes (tumour cells around fibrillary neuropil) belong to neuroblastoma and medulloblastoma, Flexner-Wintersteiner true rosettes (around a central lumen) to retinoblastoma, and perivascular pseudorosettes to ependymoma. The second recurring trap is the superlative question — most common extracranial solid tumour is neuroblastoma, most common renal is Wilms, most common hepatic is hepatoblastoma, most common intraocular is retinoblastoma — and candidates blend them into one answer. Finally, do not call stage 4S disease a typing error: disseminated disease limited to skin, liver and marrow in infants under one year can spontaneously regress, a paradox examiners enjoy testing.
Frequently asked questions
Which is the most common extracranial solid tumour of childhood?
Neuroblastoma, arising from adrenal medullary or sympathetic chain neuroblasts, with urinary VMA and HVA as the biochemical signature.
What is the triphasic pattern of Wilms tumour?
Blastemal small blue cells, tubular epithelial structures and stromal elements in one tumour; anaplastic nuclei define the unfavourable histology that changes treatment intensity.
What is special about stage 4S neuroblastoma?
In infants under one year, metastases confined to skin, liver and bone marrow may regress spontaneously without chemotherapy — the classic example of spontaneous tumour regression.
Which translocation defines Ewing sarcoma?
t(11;22)(q24;q12) generating the EWS-FLI1 fusion, with membranous CD99 positivity on immunohistochemistry.
Which tumour marker follows hepatoblastoma?
Serum alpha-fetoprotein, markedly elevated at diagnosis and used to monitor response and detect relapse.