Acute Lymphoblastic Leukaemia (ALL), Neuroblastoma, Wilms Tumour, and Management of Febrile Neutropenia

Pediatric Oncology: Leukaemias, Solid Tumours, Oncologic Emergencies, and Febrile Neutropenia

Childhood malignancies are a leading disease-related cause of death after infancy in high-income countries. Despite this, modern risk-stratified multi-agent chemotherapy and supportive care protocols have transformed pediatric oncology, achieving overall long-term cure rates approaching 85%. Because pediatric cancers frequently mimic common benign childhood illnesses during their initial stages, maintaining a high index of clinical suspicion for oncologic red flags and mastering the rapid management of acute oncologic emergencies are essential competencies tested on the European Board of Paediatrics (EBP-EAP) examination.

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Childhood Cancer Warning Signs and Diagnostic Red Flags

Unlike adult carcinomas that arise from epithelial tissues linked to environmental carcinogens, pediatric malignancies originate predominantly from uncommitted embryonic cells or hematopoietic elements. Recognizing classic warning signs enables life-saving early referral:

• Unexplained, Persistent Fever: Pyrexia of unknown origin lasting >14 days without an identifiable infectious etiology, accompanied by malaise and weight loss.
• Nocturnal Bone and Joint Pain: Bone pain that awakens the child from deep sleep, prevents ambulation, or produces a refusal to bear weight (unexplained limp). Bone pain in leukemia is caused by leukaemic blast expansion within the medullary space elevating intraosseous pressure, or subperiosteal infiltration.
• Unexplained Cytopenias and Bleeding: Pallor, progressive fatigue, unexplained petechiae, spontaneous purpura, or mucosal bleeding reflecting bone marrow replacement.
• Pathological Lymphadenopathy: Enlarged lymph nodes that are firm, rubbery, matted, non-tender, fixed to underlying tissue, or >2 cm in diameter, especially those persisting >4–6 weeks without response to antibiotics. Supraclavicular lymphadenopathy is almost invariably pathological (frequently mediastinal lymphoma or neuroblastoma).
• Neurological Red Flags: Persistent, progressive early-morning headache, headaches that wake the child from sleep, or headaches associated with projectile vomiting without nausea, visual disturbances, or ataxia (indicative of raised intracranial pressure and posterior fossa brain tumors).
• Leukocoria ("Cat's Eye" Reflex): Loss of the normal symmetrical red pupillary reflex on ophthalmoscopic examination, replaced by an abnormal white pupillary reflex. Leukocoria is the hallmark sign of retinoblastoma, the most common primary intraocular malignancy of childhood.

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Acute Lymphoblastic Leukaemia (ALL)

Acute Lymphoblastic Leukaemia (ALL) accounts for 75% to 80% of all pediatric leukaemias and represents the single most common childhood malignancy. Peak incidence occurs between 2 and 5 years of age.

Lineage and Clinical Features

• B-Cell Precursor ALL (B-ALL): Accounts for 80% to 85% of pediatric ALL cases. Originates from immature B-cell progenitors.
• T-Cell ALL (T-ALL): Accounts for 15% of cases. Predominantly affects adolescent males and classically presents with a markedly elevated initial white blood cell count and a large anterior mediastinal mass that compresses the trachea (causing respiratory distress and stridor) or the superior vena cava (Superior Vena Cava [SVC] Syndrome with facial plethora and venous distension).
• Classic Clinical Triad of Bone Marrow Infiltration:
  1. Anemia (Erythroid failure): Lethargy, progressive pallor, tachycardia, exertional dyspnea.
  2. Thrombocytopenia (Megakaryocytic failure): Petechiae, cutaneous ecchymoses, epistaxis, gingival hemorrhage.
  3. Neutropenia (Myeloid failure): Recurrent, non-resolving fevers, severe bacterial infections, oral mucosal ulcerations.
• Extramedullary Infiltration: Extramedullary blast seeding causes non-tender generalized lymphadenopathy, firm hepatosplenomegaly (in 60–70% of cases), bone tenderness, and infiltration of sanctuary sites:
  • Central Nervous System (CNS): Headache, papilledema, vomiting, and cranial nerve palsies (cranial nerves VI and VII).
  • Testicular Involvement: Painless, rock-hard unilateral or bilateral testicular enlargement (a critical site of sanctuary relapse).

Diagnostic Workup and Gold Standard Criteria

• Peripheral Blood Count and Smear: Anemia (normochromic, normocytic), thrombocytopenia, and a variable total leukocyte count (ranging from leukopenia to hyperleukocytosis >100 × 10⁹/L). Circulating lymphoblasts are present on the peripheral smear in over 85% of cases.
• Bone Marrow Aspirate (Gold Standard): Formal diagnosis requires demonstrating ≥ 20% lymphoblasts on bone marrow morphology. Blasts are characterized by high nuclear-to-cytoplasmic ratios, condensed chromatin, and inconspicuous nucleoli.
• Flow Cytometric Immunophenotyping: Establishes lineage:
  • B-ALL markers: CD19, CD10 (Common ALL Antigen / CALLA), CD22, cytoplasmic CD79a, and terminal deoxynucleotidyl transferase (TdT).
  • T-ALL markers: CD3 (cytoplasmic and surface), CD7, CD2, CD5, and TdT.

Cytogenetics and Risk Stratification

Modern pediatric oncology utilizes molecular cytogenetics to stratify therapy intensity:

Treatment Phases in Pediatric ALL

Five-year overall survival is around 90% in children with ALL; event-free survival varies by risk group. Chemotherapy spans 2 to 3 years across four continuous phases:

1. Induction (4 weeks): Aim is rapid eradication of >99% of leukaemic burden to achieve complete morphological remission (<5% marrow blasts). Three- or four-drug backbone: Vincristine, a Corticosteroid (Dexamethasone or Prednisolone), and PEG-asparaginase ± an Anthracycline (Daunorubicin) for high-risk disease.
2. Consolidation / Intensification: Eliminates residual submicroscopic leukaemic clones (cyclophosphamide, cytarabine, 6-mercaptopurine).
3. CNS-Directed Therapy: Prophylaxis against meningeal relapse. Delivered via serial intrathecal chemotherapy (methotrexate ± cytarabine ± hydrocortisone) during lumbar punctures. Cranial radiotherapy is avoided in modern protocols to eliminate secondary radiation-induced malignancies and severe neurocognitive deficits.
4. Maintenance Therapy: The longest phase (lasting until 2 to 3 years from diagnosis); continuous low-intensity outpatient therapy utilizing daily oral 6-Mercaptopurine (6-MP) and weekly oral Methotrexate, with periodic pulses of vincristine and dexamethasone.

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Tumor Lysis Syndrome (TLS)

Tumor Lysis Syndrome is a life-threatening oncologic metabolic emergency caused by the massive, spontaneous or chemotherapy-induced destruction of rapidly proliferating neoplastic cells—most frequently observed in ALL with high white cell counts, Burkitt lymphoma, and high-grade T-cell lymphoblastic lymphomas.

Metabolic Alterations (The Cairo-Bishop Criteria)

Lysis of tumor cells releases overwhelming amounts of intracellular ions and metabolites into the extracellular circulation:

1. Hyperuricemia: Catabolism of intracellular nucleic acids purines leads to massive production of uric acid by xanthine oxidase. Poorly soluble uric acid crystallizes in the acidic collecting ducts, causing acute obstructive uric acid nephropathy.
2. Hyperkalemia: Massive release of intracellular potassium (K⁺ >6.0 mmol/L) causes lethal cardiac arrhythmias (peaked T waves, PR prolongation, widened QRS, ventricular fibrillation, and asystole).
3. Hyperphosphatemia: Malignant blast cells contain up to four times more intracellular phosphate than normal lymphocytes. Excessive circulating phosphate precipitates with serum calcium into calcium phosphate crystals in the microvasculature and renal interstitium, causing acute kidney injury.
4. Secondary Hypocalcemia: Depletion of ionized calcium (Ca²⁺) due to calcium phosphate precipitation precipitates tetany, carpopedal spasm, neuromuscular irritability, seizures, and fatal cardiac conduction delays (prolonged QT interval).

                    [Massive Chemotherapeutic Cell Lysis]
                                      |
         +----------------------------+----------------------------+
         |                            |                            |
  [Nucleic Acids]                [Potassium]                  [Phosphate]
         |                            |                            |
         v (Xanthine Oxidase)         v                            v
    [Uric Acid]                 [Hyperkalemia]             [Hyperphosphatemia]
         |                            |                            |
         v                            v                            v Binds Calcium
 [Tubular Crystals]          [Lethal Arrhythmias]         [Hypocalcemia]
         |                                                         |
         +----------------------------+----------------------------+
                                      |
                                      v
                         [Acute Renal Failure & Shock]

Emergency Prevention and Management Protocol

• Intravenous Hyperhydration: The cornerstone of TLS management. Administer 2.5 to 3.0 L/m²/day (or 1.5 to 2 times maintenance) of crystalloid (0.45% or 0.9% NaCl with 5% Dextrose) WITHOUT ADDED POTASSIUM. Target high urine output: >100 mL/m²/hour (>3 mL/kg/hour in infants). Diuretics (furosemide) are reserved for fluid overload in well-hydrated patients.
• Urinary Alkalinization Caution: Routine alkalinization with sodium bicarbonate is no longer recommended; although it increases uric acid solubility, an alkaline urinary pH drastically reduces calcium phosphate solubility, promoting catastrophic calcium phosphate nephrocalcinosis.
• Uric Acid Lowering Agents:
  • Rasburicase (Recombinant Urate Oxidase): The first-line agent for patients with high-risk TLS or established hyperuricemia. Rasburicase enzymatic cleavage converts insoluble uric acid directly into allantoin, an inert, non-toxic metabolite that is 5 to 10 times more soluble in water than uric acid and rapidly excreted by the kidneys. Lowers plasma uric acid within 4 hours.
  • G6PD Deficiency Contraindication: Rasburicase produces hydrogen peroxide (H₂O₂) as an enzymatic byproduct. In patients with G6PD deficiency, the absence of reduced glutathione to neutralize H₂O₂ triggers massive, explosive hemolytic anemia and methemoglobinemia. G6PD screening is mandatory in high-risk populations prior to elective rasburicase, and rasburicase is strictly contraindicated in G6PD deficiency.
  • Allopurinol: A competitive xanthine oxidase inhibitor that blocks de novo uric acid formation. Unlike rasburicase, allopurinol does not degrade pre-existing uric acid and accumulates xanthine/hypoxanthine (risking xanthine nephropathy). Used for low-to-intermediate-risk TLS prophylaxis.

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Pediatric Solid Abdominal Tumours: Neuroblastoma vs Wilms Tumour

An abdominal mass is an important presentation of childhood solid tumours. Differentiating Neuroblastoma from Wilms Tumour (Nephroblastoma) is a classic, heavily tested scenario on the EBP-EAP examination.

Distinctive Pathognomonic Features

• Neuroblastoma:
  • Originates anywhere along the sympathetic nervous system, most commonly the adrenal medulla (40%) and retroperitoneal sympathetic chain (25%).
  • "Raccoon Eyes" (Periorbital Ecchymosis): Caused by metastatic tumor deposition within the periorbital bony orbits with obstruction of venous drainage.
  • Opsoclonus-Myoclonus Ataxia Syndrome ("Dancing Eyes, Dancing Feet"): A rare paraneoplastic autoimmune syndrome characterized by rapid, chaotic conjugate eye movements (opsoclonus), myoclonic jerking, and cerebellar ataxia.
  • Biomarkers and Staging: Over 90% of neuroblastomas synthesize catecholamines, resulting in markedly elevated urinary vanillylmandelic acid (VMA) and homovanillic acid (HVA). Amplification of the MYCN oncogene (located on chromosome 2p24) is the single most powerful biological predictor of aggressive, treatment-resistant disease.
• Wilms Tumour (Nephroblastoma):
  • The tumor is surrounded by a pseudo-capsule, typically confined to one renal flank. Gentle abdominal palpation is mandatory; rough palpation can rupture the delicate capsule, spilling tumor cells into the peritoneal cavity and upstaging the disease from Stage I to Stage III.
  • Renin-Induced Hypertension: Compression of normal juxtaglomerular renal parenchyma causes localized ischemia, stimulating excess renin secretion in up to 25% of patients.
  • Associated Syndromic Phenotypes:
    • WAGR Syndrome: 11p13 deletion involving WT1 and PAX6 (Wilms, Aniridia, Genitourinary anomalies, Range of intellectual disability).
    • Beckwith-Wiedemann Syndrome: Imprinting defect at 11p15 (macrosomia, macroglossia, hemihypertrophy, omphalocele, and neonatal hypoglycemia).
    • Denys-Drash Syndrome: Point mutation in WT1 (triad of Wilms tumor, pseudohermaphroditism / male gonadal dysgenesis, and early-onset nephrotic syndrome progressing to renal failure).

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Febrile Neutropenia: The Oncological Medical Emergency

Febrile neutropenia (FN) is the most common life-threatening oncologic complication encountered in pediatric practice. Cytotoxic chemotherapy causes profound mucosal barrier breakdown (mucositis) across the alimentary tract, allowing endogenous microflora (particularly virulent gram-negative enteric bacilli) direct access to the bloodstream. Because neutropenic patients lack white blood cells to mount classic inflammatory signs (such as erythema, swelling, or pus), fever is frequently the sole indication of overwhelming sepsis.

Clinical Definitions

• Fever: A single oral or core axillary temperature ≥ 38.3°C (101°F), OR a sustained temperature ≥ 38.0°C (100.4°F) over a period ≥ 1 hour.
• Neutropenia: An Absolute Neutrophil Count (ANC) <0.5 × 10⁹/L (<500/µL), OR an ANC <1.0 × 10⁹/L that is predicted to decline to <0.5 × 10⁹/L within 48 hours.

$$\text{ANC } (10^9\text{/L}) = \text{Total Leukocyte Count } (10^9\text{/L}) \times \left( \frac{\text{Segmented Neutrophils (\%)} + \text{Band Forms (\%)}}{100} \right)$$

Emergency Protocol: The 60-Minute Door-to-Antibiotic Window

Untreated infection during profound neutropenia can progress rapidly to septic shock and death. International pediatric oncologic protocols enforce an absolute "Door-to-Antibiotic Time" of <60 minutes:

1. Immediate Resuscitation and Access: Prioritize immediate ABCDE assessment. Access the patient's central venous catheter (port, Hickman, or PICC line) or establish prompt peripheral venous access.
2. Blood Cultures Prior to Antibiotics: Obtain blood cultures from every central venous catheter lumen; consider a concurrent peripheral culture according to local policy. Do not delay antibiotic administration for peripheral venipuncture.
3. Immediate Empiric Intravenous Monotherapy: Administer immediate broad-spectrum bactericidal antipseudomonal beta-lactam monotherapy:
   • IV Piperacillin-Tazobactam (80–100 mg/kg/dose of piperacillin; maximum 4 g piperacillin, equivalent to 4.5 g combined product), OR
   • IV Cefepime (50 mg/kg, max 2 g), OR
   • IV Meropenem (20 mg/kg, max 1 g; reserved for septic shock, intensive care admission, or known extended-spectrum beta-lactamase [ESBL] colonization).
4. Indications for Upfront Glycopeptide (Vancomycin) Addition: Add IV Vancomycin (15 mg/kg/dose) for hemodynamic instability or suspected resistant gram-positive infection, guided by local resistance and prior colonization. Examples include a clinically infected catheter tunnel/port pocket or suspected MRSA infection. Severe mucositis or recent high-dose cytarabine requires adequate viridans-streptococcal coverage; it does not by itself require vancomycin when the chosen beta-lactam already provides that coverage.
5. Absolute Clinical Contraindications:

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Lymphomas: Hodgkin and Non-Hodgkin

• When to biopsy a lymph node: persistent or enlarging nodes, supraclavicular nodes, hard, matted or fixed nodes, or nodes accompanied by systemic symptoms, an abnormal chest radiograph or an abnormal blood count.
• Hodgkin lymphoma peaks in adolescence. It presents with painless, rubbery cervical or supraclavicular lymphadenopathy, often with a mediastinal mass. B symptoms, which are used in staging, are unexplained fever above 38.0°C, weight loss of 10% or more in the preceding 6 months, and drenching night sweats; pruritus can occur. Classical disease shows Reed–Sternberg cells, and Epstein–Barr virus is associated with some cases. Risk-adapted chemotherapy, with or without radiotherapy, cures most children.
• Childhood non-Hodgkin lymphoma is usually high grade. Burkitt lymphoma is a rapidly growing abdominal mass (it can cause ileocaecal intussusception in an older child) with a high risk of tumour lysis syndrome. Lymphoblastic lymphoma, usually T-cell, often presents with an anterior mediastinal mass. Anaplastic large-cell and diffuse large B-cell lymphomas also occur.
• Anterior mediastinal mass emergency: orthopnoea, stridor, wheeze, dysphagia or facial and neck swelling signal airway or superior vena cava compression. General anaesthesia, deep sedation or lying flat can cause fatal airway or circulatory collapse, so obtain the diagnosis by the least invasive route (blood, pleural fluid, bone marrow or a peripheral node under local anaesthesia). Corticosteroids or radiotherapy before biopsy are reserved for life-threatening compression because they can obscure the diagnosis.

Sources: NCI PDQ Childhood Hodgkin Lymphoma Treatment; NCI PDQ Childhood Non-Hodgkin Lymphoma Treatment.

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Principles of Paediatric Palliative Care

• Palliative care for children is the active total care of the child's body, mind and spirit, with support for the family. Ideally it starts at diagnosis, which may be at birth, and continues whether or not the child receives treatment directed at the disease. It needs a multidisciplinary team.
• It applies to life-limiting and life-threatening conditions such as cancer, severe neurodisability, complex congenital heart disease and progressive metabolic or neuromuscular disease. Parallel planning prepares for both improvement and deterioration.
• Advance care planning with the child or young person and parents covers goals of care, the preferred place of care and death (home, hospice or hospital) and resuscitation decisions, which must be recorded and shared with everyone involved.
• Symptom management covers pain (regular analgesia by mouth where possible; avoid intramuscular injections), breathlessness, nausea and vomiting, seizures, secretions, agitation and opioid-induced constipation, with anticipatory medicines available at home.
• Provide honest, developmentally appropriate communication, psychological, spiritual and practical support, respite, support for siblings, and bereavement support that continues after death.

Sources: WHO/Europe palliative care for children; NICE NG61 end of life care for infants, children and young people.