Presentation A woman brings her 5-year-old son to your office after noticing a “lump” in his abdomen while hugging him. He hasn’t complained of abdominal pain or nausea and has no changes in his urine or stool. His mom also denies fever, rash, and cold symptoms.

History Past Medical Hx: None Birth Hx: Term infant, SVD, no forceps or vacuum used, mother had standard prenatal care without any complications, infant was discharged with mother at 48 hours Developmental Hx: Normal per Mom Immunizations: UTD Family Hx: Mom is healthy, Dad has HTN, 3-year-old sister and 18-month-old brother are healthy, paternal grandfather has DM and HTN Social Hx: Lives with parents and 2 younger sibs, goes to pre- kindergarten, has a kitten, no one smokes in the home Allergies: Penicillin (rash) Medications: None

Physical Exam Vitals: – T 37 ⁰C – BP 95/54 – HR 95 – RR 22 – O2 100% on room air General: non-toxic, alert, interactive HEENT: PERRL, EOMI, moist oral mucosa, no exudates CV: RRR, no murmur Resp: CTAB, no crackles or wheezes Abd: Non-distended; firm, nontender, fixed mass on the right that does not cross the midline; normal bowel sounds GU: Normal genitalia for age MS: moves all 4 extremities, normal tone Neuro: CN II-XII grossly intact, reflexes 2+, normal finger-to-nose testing, normal gait

Differential Diagnosis for Abdominal Mass Hepatobiliary – Hepatoblastoma – Hepatocellular carcinoma – Choledochal cyst – Benign liver tumor Renal – Hydronephrosis – Polycystic kidney – Wilms tumor – Rhabdoid tumor Retroperitoneal – Neuroblastoma – Teratoma – Lymphoma – Rhabdomyosarcoma GI – Intussusception – Duplication cyst – Constipation – Hirschsprung disease GU – Testicular neoplasm – Undescended testicle – Bladder obstruction

Laboratory Tests Urinary VMA: neg Urinary HVA: neg CBC: CMP: < UA: moderate RBC AST 32 ALT 29 Alk phos 125 Total protein 7.0 Albumin 4.5 Total bili 1.1

Imaging Ultrasound revealed an intraabdominal mass on the right. CT was ordered and is shown below.

Histologic Confirmation of Diagnosis Biopsy revealed a triphasic combination of stromal (fibrocytic, myxoid, skeletal muscle components), blastemal (small blue cells), and epithelial (tubules, glomeruli) cell types. Focal anaplasia, shown on right, is seen in approximately 5%.

Gross Morphology The mass was subsequently resected. It was large, soft, well-circumscribed, homogenous, and tan in color.

What is your final diagnosis?

Wilms tumor Aka nephroblastoma Embryonal malignancy of the kidney Most cases are sporadic but 1-2% are familial May arise in 1 or both kidneys Associated with the following syndromes: – WAGR (aniridia, GU abnormalities, mental retardation) – Denys-Drash syndrome (early-onset renal failure, male pseudohermaphrodism) – Beckwith-Wiedemann syndrome (organomegaly, macroglossia, omphalocele, hemihypertrophy)

Epidemiology 2 nd most common malignant abdominal tumor in childhood Incidence is approximately 8 in 1 million children younger than age 15 About 500 new cases in North America per year Peak incidence between ages 2 and 5 Individual with horseshoe kidney have twice the risk

Initial Presentation Many children present with an asymptomatic abdominal mass 1/3 have intermittent abdominal pain that may have been exacerbated by trauma 1/4 have gross or microscopic hematuria and is usually painless 1/4 have HTN Systemic symptoms may occur, especially if there is bleeding into the tumor and associated anemia About 10% will show pulmonary metastases at the time of diagnosis

Treatment National Wilms Tumor Study – Stages I & II w/ favorable histology: surgical resection followed by 19 weeks of chemotherapy – Stages I & II w/ anaplastic histology: surgical resection followed by 19 weeks of chemotherapy and radiation therapy – Stage III: surgical resection followed by 24 weeks of triple drug chemotherapy and radiation therapy – Stage IV: surgical resection followed by 24 weeks of triple drug chemotherapy plus radiation therapy to the abdomen and lungs for mets International Society of Pediatric Oncology – Stage I: pre-op chemotherapy for 4 weeks, surgical resection, post-op chemotherapy for 4 weeks – Stage II: pre-op chemotherapy for 4 weeks, surgical resection, post- op triple drug chemotherapy for 27 weeks – Stage III: pre-op chemotherapy for 4 weeks, surgical resection, post- op triple drug chemotherapy for 27 weeks plus radiation therapy – Stage IV: pre-op triple drug chemotherapy for 6 weeks, surgical resection, post-op triple drug chemotherapy for 9 weeks—if remission is achieved continue to 27 weeks, if not add additional chemotherapeutic agents for an additional 34 weeks and add radiation therapy

Prognosis Determined by tumor histology, stage, and molecular/genetic markers Overall survival approaches 90% with either treatment protocol Patients with diffuse anaplastic tumor have the worst prognosis Approximately 15% with favorable histology and 50% with anaplastic features have tumor recurrent disease, most often involving the lung