Extrarenal Wilms\' tumour

Clinical History

A 5-year-old boy with no relevant personal or family medical history was admitted at the emergency department with dysuria and hypogastric pain with 24 hours of evolution. On physical examination a hard painful mass in the right flank and right iliac fossa was noted and therefore the patient underwent abdominal ultrasound and CT.

Imaging Findings

Abdominal sonography demonstrated a solid heterogeneous well-defined mass, without calcification, with small cystic areas, located above the bladder.

Abdominal CT showed a large lobulated, soft tissue density mass in the pelvic region. The mass was heterogeneous, with extensive hypodense areas reflecting necrosis. No evidence of calcification was seen in the lesion. The mass extended from the aortic bifurcation making contact with the bladder, but without definite signs of invasion. There were no signs of bone invasion. Both kidneys were normal.

The following complementary exams were performed: Tru-cut biopsy (inconclusive), tumour markers - alpha-fetoprotein, beta-HCG - and urinary catecholamines (normal), bone scintigraphy (normal) and myelogram (normal).

Since the results were inconclusive the child underwent surgical biopsy and the diagnosis of extrarenal nephroblastoma was established.

Surgical resection, chemotherapy and neoadjuvant radiotherapy were performed.

Discussion

Wilms' tumour (also referred to as nephroblastoma) is the most common genitourinary tract tumour in children. It is an embryonic malignant tumour composed of varying amounts of kidney embryonic elements [1, 2].

Its extrarenal location is extremely rare and poorly understood. So far only a few isolated cases were described in literature [3, 4].

It can occur in various locations and clinical presentation is nonspecific and dependent on the tumour location. It is almost always difficult to diagnose it preoperatively.

Most cases have occurred in the retroperitoneum and inguinal canal. It can also affect uterus, cervix, testis, epididymis, skin and even the thorax. Renal Wilms' tumour generally occurs before the age of 10. Likewise, most extrarenal cases also occur in young patients [3-5].

The diagnosis of extrarenal Wilms' tumour excludes, by definition, a primary tumour of the kidney. Therefore it is important to exclude a primary tumour of the kidney with extrarenal metastases or the presence of a supernumerary kidney. However, the final diagnosis is established by histopathology [4-8].

The intrarenal Wilms' tumour originates from metanephric blastema, but its extrarenal origin is much more controversial. Most advocate a similar origin to the intrarenal tumour occurring in heterotopic foci of metanephric blastema, others argue a mesonephric origin, and still others defend the malignant transformation of cells with persistent embryonic potential [6-9].

The imaging presentation of extrarenal Wilms' tumour is similar to intrarenal Wilms' tumour.
CT and MRI provide characterization of the mass, its local extension and additionally allow detection of distant metastases [7-9].

Nowadays there is no accepted staging system for extrarenal Wilms' tumour, so the system NWTS (National Wilms Tumor Study), which has the largest number of documented cases, has been used [2-4,10].

The recommended management of true extrarenal Wilms' tumour includes a thorough staging, detailed pathologic classification, post-operative chemotherapy and radiotherapy [8-9,11].

The prognosis is comparable to intrarenal Wilms' tumour.

Differential Diagnosis List

Final Diagnosis

Extrarenal Wilms' tumour

URL:	https://www.eurorad.org/case/9556
DOI:	10.1594/EURORAD/CASE.9556
ISSN:	1563-4086