What is the presentation, diagnosis, and management of pediatric abdominal masses?

Pediatric Abdominal Mass: Presentation, Diagnosis, and Management

Clinical Presentation

Pediatric abdominal masses present with age-specific patterns and symptoms that directly guide differential diagnosis, with neonates typically presenting with renal or retroperitoneal masses, while older children more commonly present with lymphomas or germ cell tumors. 1

Age-Specific Presentations

• Neonates and infants: Most commonly present with renal masses (hydronephrosis, multicystic dysplastic kidney, Wilms tumor) or hepatic masses (hepatoblastoma, hemangiomas) 1, 2
• Young children (1-5 years): Neuroblastoma and Wilms tumor predominate, often presenting as large, asymptomatic masses discovered incidentally 2, 3
• Older children and adolescents: Lymphomas, germ cell tumors, and ovarian masses become more common 2, 4

Symptom Patterns by Tumor Type

Renal masses (Wilms tumor, cystic nephroma):

• Abdominal mass or distention (most common presentation) 5
• Hematuria (less common) 5
• Hypertension in some cases 2

Hepatic masses (hepatoblastoma):

• Abdominal pain or swelling 5
• Poor appetite and early satiety 5
• Constitutional symptoms (fever, weight loss) 5

Lymphomas (Burkitt, DLBCL):

• Fever, night sweats, unexplained weight loss 5
• Abdominal pain/swelling, nausea/vomiting, constipation 5
• Painless lymphadenopathy 5
• Oncologic emergencies: tumor lysis syndrome, superior vena cava syndrome, respiratory compromise, spinal cord compression 5

Ovarian masses:

• Abdominal pain or palpable mass 4
• Menstrual irregularities 4
• Signs of virilization (voice changes, hirsutism, premature acne) in sex cord-stromal tumors 5, 4
• Nausea and vomiting 4

Acute presentations requiring immediate attention:

• Respiratory distress, chest pain (suggests mediastinal extension or pleural involvement) 5
• Bladder/bowel dysfunction, lower extremity weakness (CNS or spinal cord involvement) 5
• Severe abdominal pain (possible torsion, rupture, or hemorrhage) 3

Differential Diagnosis by Anatomic Location and Age

Systematic Approach to Differential

The anatomical location of the mass, patient age, and associated symptoms must be considered together to formulate differential diagnoses. 3

Upper Abdomen Masses

Hepatic origin:

• Infants: Infantile hepatic hemangioma (especially with ≥5 cutaneous hemangiomas), hepatoblastoma 5
• All ages: Hepatoblastoma (peak 1-3 years), hepatocellular carcinoma (rare), benign cysts 5, 6

Splenic origin:

• Lymphoma, cysts, abscess 6

Flank/Retroperitoneal Masses

Renal origin:

• Neonates: Hydronephrosis, multicystic dysplastic kidney, congenital mesoblastic nephroma 1, 2
• 1-5 years: Wilms tumor (peak incidence), cystic nephroma 5, 2
• All ages: Renal cell carcinoma (rare in children) 2

Adrenal/retroperitoneal origin:

• Neuroblastoma (most common in children <5 years) 2
• Adrenal hemorrhage (neonates) 1

Lower Abdomen/Pelvic Masses

Ovarian origin (females):

• Prepubertal: Functional cysts, mature teratoma (most common neoplasm), dysgerminoma (most common malignancy) 4
• Adolescents: Functional cysts, mature teratoma, endometrioma, sex cord-stromal tumors 4

Gastrointestinal origin:

• Mesenteric/omental cysts 6
• Lymphoma (especially Burkitt) 5
• Duplication cysts 6

Genitourinary origin:

• Germ cell tumors (sacrococcygeal teratoma in neonates) 2
• Rhabdomyosarcoma (bladder, vagina) 5

Midline/Diffuse Masses

• Lymphoma (Burkitt, DLBCL, lymphoblastic) 5
• Mesenteric adenitis (benign) 3
• Organomegaly (hepatosplenomegaly in leukemia/lymphoma) 5

Diagnostic Workup

Initial Imaging Algorithm

Ultrasonography is the optimal initial screening tool for pediatric abdominal masses—it is widely available, lacks ionizing radiation, requires no sedation, and has high sensitivity for detecting masses. 5, 1

Ultrasound Protocol

• Doppler ultrasound of abdomen should be performed initially to establish mass presence, origin, and vascularity 5, 1
• No fasting required for abdominal/renal ultrasound 5
• Assess for solid vs. cystic components, vascularity, and relationship to surrounding structures 1

Key ultrasound features suggesting malignancy:

• Solid components, large size, heterogeneous appearance 4
• Lobulated margins, chunky calcifications 5
• Heterogeneity indicating hemorrhage or necrosis 5
• Diminished vascularity (in hepatic masses) 5

Advanced Imaging Indications

MRI without and with IV contrast is preferred for further characterization when:

• Ultrasound findings are indeterminate 5, 1
• Presurgical planning is needed (especially for nephron-sparing surgery in Wilms tumor) 5
• Detection of multiple tumors or nephrogenic rests is required 5
• Superior lesion characterization needed (multiphase contrast enhancement, diffusion-weighted imaging) 5

CT with IV contrast may be used when:

• MRI is unavailable or contraindicated 5
• Rapid assessment is needed in unstable patients 1
• Note: MRI is preferred over CT due to lack of ionizing radiation 5

Chest imaging (CT chest preferred):

• Essential for staging lymphomas and metastatic disease 5, 1
• Initial chest CT recommended between 3-6 months for DICER1 syndrome surveillance 5

Laboratory Evaluation

Tumor markers are essential but cannot confirm or exclude malignancy—they must be interpreted with imaging and clinical context. 4

Essential Tumor Markers

Alpha-fetoprotein (AFP):

• Elevated in hepatoblastoma, germ cell tumors (yolk sac tumor) 5, 4
• Critical: AFP values in infants must be interpreted using age-specific reference ranges (normally elevated in first years of life) 5
• Surveillance protocol: Monitor AFP trend over time; large rises (>50-100 ng/mL) require repeat testing in 6 weeks and re-examination of recent imaging 5
• Significant elevations (>1000 ng/mL): Validate immediately and proceed directly to advanced imaging (MRI preferred) 5

Beta-hCG (human chorionic gonadotropin):

• Elevated in germ cell tumors (choriocarcinoma, embryonal carcinoma) 4

Lactate dehydrogenase (LDH):

• Elevated in lymphomas, germ cell tumors (dysgerminoma) 4

Cancer antigen 125 (CA-125):

• May be elevated in epithelial ovarian tumors 4

Inhibin:

• Elevated in sex cord-stromal tumors 4

Catecholamines (urine VMA/HVA):

• Elevated in neuroblastoma 2

Hematologic Workup

Complete blood count with differential:

• Assess for cytopenias suggesting bone marrow infiltration (leukemia/lymphoma) 5
• Peripheral blood may substitute for bone marrow if ≥1,000 circulating lymphoblasts/μL or ≥20% lymphoblasts present 5

Bone marrow aspirate and biopsy:

• Required for leukemia diagnosis (≥20% lymphoblasts) 5
• Essential for lymphoma staging 5

Tissue Diagnosis

Excisional or incisional biopsy of the most accessible site is preferred, with fresh tissue sent in saline to ensure viability for comprehensive pathologic evaluation. 5

Biopsy Protocol

• Touch preparation for cytologic examination recommended 5
• Morphologic and immunohistochemistry review performed as clinically indicated 5
• Immunophenotyping and cytogenetics essential for lymphoma diagnosis 5
• Minimum diagnostic methodologies: Morphology and flow cytometry, especially if patient is critically ill 5
• Malignant fluid cytology and flow cytometry may suffice in urgent situations 5

Important caveat: Definitive diagnosis may not be feasible before beginning treatment in critically ill patients 5

Management Principles

General Approach

All pediatric patients with suspected malignant abdominal masses should be treated at specialized cancer centers with expertise in pediatric oncology to ensure optimal outcomes and avoid unnecessary procedures. 5

Tumor-Specific Management

Wilms Tumor and Cystic Nephroma

Nephron-sparing surgery is recommended whenever possible in syndromic Wilms tumor due to increased recurrence risk in ipsilateral or contralateral kidney. 5

• Preoperative MRI is ideal for detecting multiple tumors, nephrogenic rests, and planning partial nephrectomy 5
• Factors favoring complete nephrectomy: Infiltration of adjacent structures, central location, tumor thrombus, tumor rupture, collecting system involvement 5

Hepatoblastoma

Surveillance protocol for high-risk syndromes (Beckwith-Wiedemann, Isolated Hemihypertrophy, Trisomy 18, Simpson-Golabi-Behmel):

• Abdominal ultrasound every 3 months from birth through age 4 years 5
• AFP monitoring every 3 months, interpreted using BWS-specific reference ranges 5

Diagnostic workup for suspected hepatoblastoma:

• Rising AFP values (>50-100 ng/mL increase): Repeat AFP in 6 weeks and re-examine recent ultrasound 5
• Two successive AFP increases: Proceed to MRI with hepatobiliary contrast agent 5
• Contrast-enhanced ultrasound is emerging as alternative tool 5

Lymphomas (Burkitt, DLBCL)

Oncologic emergencies require immediate recognition and management:

• Tumor lysis syndrome, superior vena cava syndrome, respiratory compromise, spinal cord compression 5
• Treatment may need to begin before definitive diagnosis in critically ill patients 5

Staging workup:

• Bone marrow aspirate and biopsy 5
• CNS evaluation (lumbar puncture with cytology) 5
• Chest CT for mediastinal involvement 5

Ovarian Masses

Management must balance curative intent with fertility preservation—treatment should be function-preserving and minimally invasive when feasible. 4

Risk stratification for malignancy:

• High-risk features: Solid components, large size, heterogeneous appearance on imaging; elevated tumor markers (AFP, LDH, beta-hCG, CA-125, inhibin) 4
• Most common pediatric ovarian neoplasm: Mature teratoma (benign) 4
• Most common pediatric ovarian malignancy: Dysgerminoma 4

Surveillance Recommendations for Predisposition Syndromes

DICER1 Syndrome

Abdominal ultrasound surveillance:

• Biannual from birth through age 8 years (for cystic nephroma and Wilms tumor) 5
• Annual from age 8 years onward (Wilms tumor reported up to age 13 years) 5

Pelvic ultrasound surveillance:

• Annual or semiannual throughout childhood and adulthood (for ovarian sex cord-stromal tumors and cervical rhabdomyosarcoma) 5

Thyroid ultrasound:

• Starting at age 8 years, repeat every 3 years if normal 5

Chest imaging:

• Initial chest CT between 3-6 months of age 5
• Second chest CT between 2.5-3 years if initial normal 5
• Consider every-6-month chest radiographs until age 8 years, then annual through age 12 years 5

Beckwith-Wiedemann Syndrome/Isolated Hemihypertrophy

Abdominal ultrasound: Every 3 months from birth through age 4 years 5

AFP monitoring: Every 3 months from birth through age 4 years 5

Critical Pitfalls to Avoid

• Do not delay referral to specialized pediatric oncology centers—early involvement improves outcomes 5, 3
• Do not interpret AFP values using standard pediatric reference ranges in infants—use age-specific and syndrome-specific values 5
• Do not perform unnecessary oophorectomies in adolescents—fertility preservation is paramount when oncologically safe 4
• Do not assume benign disease based on imaging alone—tissue diagnosis is essential for definitive management 5, 1
• Do not overlook oncologic emergencies—tumor lysis syndrome, respiratory compromise, and spinal cord compression require immediate intervention 5