Wilms tumoru with bony-mandibular, rib and calvarial metastases

Clinical History

3-year-old boy presented with a lump in the abdomen on the right side, abdominal pain, and increasing abdominal girth during the past 6 months.

Imaging Findings

USG revealed a solid right renal mass. CECT showed a heterogenously enhancing solid mass with few tiny calcifications in the upper pole, interpolar region of the right kidney, compressing and displacing the remaining renal parenchyma, forming a pseudocapsule/claw around it (claw sign). Renal vein, IVC were pushed anteriorly, aorta to the left. Right renal vein showed partial lumen occluding filling defect (thrombus). Findings were consistent with Wilms tumour. Opposite kidney was normal. The other findings were small lytic lesions with periosteal reaction in the ramus of the left mandible, lytic lesion in right second rib with large adjacent soft tissue extending into the right pleural space, nodule in adjacent lung parenchyma, lytic lesion with associated soft tissue in the right half of the frontal bone, enlarged right adrenal with a heterogeneously enhancing lesion within and two heterogeneously enhancing lesions in the liver.
On histopathology the mass showed undifferentiated blastemal cells, few differentiated glomerular structures, mesenchymal tissues and tubules, consistent with Wilms tumour.

Discussion

Wilms (nephroblastoma) accounts for 87% of paediatric renal masses. Its peak incidence is at 3–4 years of age, 80% of patients present before 5 years [1]. It arises from mesodermal precursors of the renal parenchyma (metanephros). Chromosome 11 (WT1: 11p13, WT2: 11p15), loci on chromosomes 1, 8, 12 affection are found. Most cases are sporadic, 2% of cases are familial. They are unilateral in 95 % cases. Some familial syndromic associations are Beckwith Wiedemann, WAGR, Drash syndrome [1].
Patient presents with painless abdominal mass and haematuria.
On plain abdomen X-ray a large soft tissue opacity is usually seen displacing the bowel inferiorly. Ultrasound confirms the solid nature of the mass, distinguishes it from hydronephrosis and cystic renal masses. Doppler assesses renal vein, IVC for tumour thrombus. CT/MRI are needed for accurate staging [2]. On CT they appear as intrarenal heterogeneously enhancing solid masses surrounded by a compressed rim of renal parenchyma. They displace adjacent structures like aorta and its branches without encasing/invading them. When large these tend to cross the midline. Tumour thrombus may extend into the renal vein, IVC, right atrium. Calcification, fat may be seen rarely. MRI assesses IVC involvement accurately. It metastasizes most commonly to the lung (85%), liver, lymph nodes. Bony metastases are very rare in Wilms tumour and are associated with a poorer prognosis [3].
Staging is surgical (National Wilms tumour study group). Stage I (confined to kidney), II (extension beyond kidney but limited capsular, renal vein, sinus involvement, completely resected) are treated by combination of chemotherapy to downstage the tumour followed by resection (complete nephrectomy). Stages III (lymph nodal, peritoneal spread, incomplete resection), IV (haematogenous, lymph nodal metastastes outside abdomen) are treated with chemoradiotherapy. In Stage V (synchronous bilateral) preoperative chemotherapy is important. Complete resolution of disease in one kidney may allow surgery on the contralateral kidney. Each kidney is staged individually, followed by partial nephrectomy. Local radiation therapy of the tumour bed is advocated in some cases, complete abdominal irradiation can be used when there is gross tumour spillage at surgery or peritoneal tumour implantation [1]. Recurrence can be within the tumour bed, as well as distally.
Our patient, with stage IV Wilms, underwent nephrectomy followed by chemotherapy (actinomycin-D, doxorubicin, cyclophosphamide, carboplatin, etoposide) for 6 weeks, radiotherapy to abdomen and thorax. Unfortunately during the chemotherapy, the patient succumbed to chest infection. From the overall clinical course of the patient we could conclude that bony metastases in Wilms are a poor prognostic factor.

Differential Diagnosis List

Final Diagnosis

Wilms tumor with distant metastases (mandibular, rib, pleural, lung, liver, adrenal).

URL:	https://www.eurorad.org/case/13429
DOI:	10.1594/EURORAD/CASE.13429
ISSN:	1563-4086