Radiology

Case of the Month

Radiological Findings

Discussion

Case Report:

A one- year-old girl was brought with complaints of a lump in the abdomen and failure to thrive since two months.

On examination, there was a huge firm, non-tender, smooth mass involving the left side of the abdomen which was not crossing the midline. The mass did not move with respiration.

Routine laboratory tests were within normal limits.

 

RADIOLOGICAL FINDINGS:

Ultrasound:

Ultrasound examination of the abdomen showed a well defined mass with heterogenous echotexture arising from the left kidney. It had displaced the kidney medially with distortion of the pelvicalyceal system. The left renal vein and the inferior vena cava (IVC) were normal.

CT ABDOMEN (fig. 1a to fig.1d )

Plain axial CT abdomen showed a well-circumscribed, encapsulated, heterogenous predominantly hypodense (HU value ranging from -26 to- 5 Hounsefield unit) mass lesion arising from the mid pole of the left kidney which displaced the kidney medially.

On contrast administration, it showed heterogenous enhancement. There was no extension of the tumor into the renal vein or IVC. There was no intra abdominal lymphadeonopathy or evidence of metastases. Delayed images showed splaying of the pelvicalyceal system by the mass.

MRI Abdomen : ( Fig 2a and 2b)

T2W TRUFI coronal and axial images confirmed the findings on the CT scan.

T1 W inphase and outphase images showed loss of signal on outphase image which is seen in inphase image confirming that it is a fat containing lesion

The radiological differential diagnosis included Angiomyolipoma, Wilm’s tumor and a leiomyoma.

On the basis of these findings the tumor was operated . Enblock removal of tumor with left total nephrectomy was performed. The specimen was sent for pathological examination..

Fig. 3a	Fig. 3b

 

Gross specimen and histopthology (Fig 4a and 4b)

Gross cut section of the specimen shows encapsulated mass arising from kidney .It shows fat containing foci within.

Final diagnosis on histopathology is suggestive of triphasic variant Wilm’s tumor showing epithelial, blastemal and stromal elements along with fat cells .

Currently patient is undergoing intermittent cycles of chemotherapy.

DISCUSSION:

Wilm’s tumor (WT) is the fifth most common pediatric malignancy and the most common abdominal renal tumor in children.

It is tumour arising from persistent primitive metanephric blastemal elements.

Incidence & etiology:

- 7to 8 cases per million children per year.

- When associated with syndromes age at tumor occurrence younger.

- Only 2% of wilm’s tumor s are familial.

Most cases are not part of a genetic malformation syndrome and have no familial history; however, familial Wilm’s tumor arises with high frequency in certain families.

Presentation :

Wilm’s tumor is diagnosed at a mean age of 3.5 years. The most common feature at presentation is an abdominal mass. Abdominal pain occurs in 30%-40% of cases. Other signs and symptoms of Wilm’s tumor include hypertension ,fever caused by tumor necrosis, , and anemia.

Major congenital anomalies include genitourinary anomalies (WAGR and Denys-Drash syndromes, 5% of cases), ectopic solitary horseshoe kidney, hypospadias and cryptorchidism, hemihypertrophy and organomegaly (Beckwith-Wiedemann syndrome, 2% of cases); and aniridia (1% of cases). Children with such syndrome anomalies should undergo periodic testing for Wilm’s tumor. Ultrasonography of the kidneys (once or twice per year) is a good screening tool.

Imaging Studies

Ultrasound

Ultrasound is the primary modality for evaluating the site of origin ,size , extent and architexture of the tumor. Cystic areas within the mass seen both on US and CT contribute to the nonhomogenous appearance and these develop because of tumour necrosis or deposition of mucin.

Renal vein or IVC tumor extension which is seen in 5 % of patients.

CT Scan

CT scan helps to differentiate a kidney tumor from an adrenal tumor (neuroblastoma)

To rule out Liver metastases

Status of chest with respect to metastases

Status of opposite kidney

Lymph node assessment

Chest XR

As a baseline for pulmonary metastases (the lung is the most common site of distant metastasis ).

MRI

The value of MRI in diagnosing this disorder is yet to be established.

Useful for MRV to aid in the diagnosis of thrombus of the renal vein or IVC.

Differential Diagnosis:

1) Angiomyolipoma.

Contains fat and enhance with contrast

Associated with Tuberous sclerosis .

2) Neuroblastoma: Wilm’s tumor seldom extends behind the aorta as neuroblastoma does .

Neuroblastoma is uniformly solid and homogenous

Tumor extends into the chest (Thoraco-abdominal sign)

Mets to bone more often .

3) Multifocal renal nephroma:

Similar age of distrubition and can resemble cystic wilm’s tumor .

4) Clear cell sarcoma and rhabdoid tumor of the kidney :

It was once considered aggressive form of Wilm’s tumor and is identical to it on imaging .

Rhabdoid tumors are typically diagnosed in infancy (<1 yr)

Clear cell sarcomas frequently have skeletal metastases at the time of diagnosis.

5) RENAL CELL CARCINOMA :

Occurs in older children .It is rare before the age of 6 years.

 6) CONGENITAL MESOBLASTIC NEPHROMA

 7) RENAL MEDULLARY CARCINOMA.

Seen in adolescents with sickle cell trait or disease

Staging (National Wilm’s Tumor Study)

Stage I: Tumor limited to the kidney and completely excised. The renal capsule is intact and the tumor was not ruptured before removal. There is no residual tumor

Stage II :Tumor extends through the perirenal capsule but is completely excised. There may be local spillage of tumor confined to the flank, or the tumor may have been biopsied. Extrarenal vessels may contain tumor thrombus or be infiltrated by tumor

Stage III: Residual nonhematogenous tumor confined to the abdomen: lymph node involvement, diffuse peritoneal spillage, peritoneal implants, tumor beyond surgical margin either grossly or microscopically, or tumor not completely removed.

Stage IV: Hematogenous metastases to lung, liver, bone, brain, or other organ

Stage V: Bilateral renal involvement at diagnosis.

Surgical Treatment:

Is dependant on the stage of the tumour.

Prognosis

Approximately 80-90% of diagnosed children survive with current multimodality therapy.

Patients with FH tumors have at least an 80% overall survival rate at 4 years after initial diagnosis, even in patients with stage IV disease.

Synchronous bilateral cases have a 70-80% survival rate, while those with metachronous tumors have a 45-50% survival rate.

The prognosis for patients who relapse is poor, with only 30-40% expected to survive after retrieval therapy.