Differentials
Neuroblastoma
SIGNS / SYMPTOMS
May have failure to thrive, skin metastasis, exophthalmos, or periorbital ecchymoses.[74][75][76]
INVESTIGATIONS
Urine catecholamines are elevated.[75]
CBC showing anemia, neutropenia, or thrombocytopenia may suggest bone marrow infiltration in advanced stage IV neuroblastoma.[77]
Tumor cytogenetics shows MYCN gene amplification.[78]
Neuroblastoma is heterogeneous in appearance on abdominal ultrasound and typically shows calcifications. It rarely shows tumor extension into the lumen of the renal vein and inferior vena cava.[75]
Meta-iodobenzylguanidine (MIBG) scintigraphy usually shows MIBG accumulation.[79]
Clear cell sarcoma of the kidney
INVESTIGATIONS
Doppler ultrasound of abdomen followed by CT or MRI usually reveals unicentric renal mass originating from renal medulla and involving the entire kidney.
Histology is diagnostic: mucopolysaccharide matrix which gives the classic "clear" appearance, fibrovascular septa, and small cord cells.[81]
Typical cytogenetic findings include BCOR internal tandem duplications and YWHAE-NUTM2B fusions.[81][82]
Bone scan or PET scan may show bone metastases.[81]
Renal cell carcinoma
SIGNS / SYMPTOMS
Patients are usually older at presentation.[83]
May rarely be associated with Von Hippel-Lindau syndrome or other rare hereditary syndromes.[83]
INVESTIGATIONS
Histologically, tumor cells form papillae, tubules, or nests. In pediatric renal cell carcinoma, microphthalmia transcription factor translocation is the most common subtype, with mixed histologic appearance, with or without calcifications, and often with psammoma bodies.[83]
Tumor cells may appear "clear" due to accumulation of lipids and glycogen. Surrounding parenchyma may form a pseudocapsule due to compression.
Malignant rhabdoid tumor of the kidney (RTK)
SIGNS / SYMPTOMS
Age at presentation is typically <2 years of age.[84]
Stage 3 and 4 disease are prevalent.[84][85]
Neurologic deficits secondary to metastatic disease, or associated second primaries linked to germline SMARCB1 mutations (hereditary rhabdoid tumor predisposition), occur in 10% to 15% of RTK patients.[84][86][85]
Polycystic kidney disease
SIGNS / SYMPTOMS
Autosomal-recessive form can present with renal failure in early infancy.[88]
Autosomal-dominant form usually presents in adulthood and may present with anuria or renal failure.[88]
Hypertension is more common.
INVESTIGATIONS
Kidneys are generally enlarged and demonstrate multiple irregular cysts on ultrasound.
Extrarenal cysts (e.g., liver, pancreas, and spleen) help confirm diagnosis.[88]
Congenital mesoblastic nephroma (CMN)
Pheochromocytoma
SIGNS / SYMPTOMS
Occurs in older children ages 6-14 years.[92]
Other symptoms may include palpitations, diaphoresis, and nervousness or anxiety.
Paroxysmal hypertension, tachycardia, and tremor may also be present.
INVESTIGATIONS
Urine and serum catecholamines are elevated.[92]
Ultrasonography detects larger tumors easily. To better define the location and extent, a contrast CT or MRI, should be obtained.
Accumulate meta-iodobenzylguanidine (MIBG) avidly; therefore, MIBG scintigraphy is used for tumor surveillance, and to identify extra-adrenal pheochromocytomas.[92]
Burkitt lymphoma
SIGNS / SYMPTOMS
More common in males and mean age of presentation is 7 years.
Ascites, generalized lymphadenopathy, pancytopenia, and tumor lysis syndrome present.
INVESTIGATIONS
CT scan usually reveals a lobulated heterogenous mass with areas of necrosis. Tumor may involve adjacent bowel and mesentery.[93] Renal involvement is often multifocal.
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