Wilms tumor in horseshoe kidney

Case contributed by Dr Hazem M Almasarei

Presentation

Abdominal mass.

Patient Data

Age: 2 years
Gender: Male
Ultrasound

Large mixed echogenicity soft tissue mass located in the retroperitoneum of the mid abdomen.

There is a large lobulated heterogeneous density mass lesion with areas of necrosis/cystic density arising from a horseshoe kidney (involving the right kidney more than the left by claw sign). It compresses the right renal pelvis resulting in moderate hydronephrosis. The right kidney itself appears hypoattenuating in comparison with the left one, probably due to a delayed nephrogram. There is a suspicious of anterior abdominal wall invasion, as well as of the right liver lobe. The mass compresses the adjacent vessels without invasion or tumoral thrombus. There is non-specific mild stranding of the surrounding fat planes. Features are in keeping with a Wilms tumor.

After chemotherapy, significant partial response exceeding 60-70%. No definite evidence of liver infiltration or abdominal wall involvement. 

Case Discussion

Pathology report:

Tissue origin: Right kidney.
Gross description: Specimen Type: Radical nephrectomy Laterality: Right Kidney Size: Kidney dimension: 7.5 x 6 x 3.5 cm Weight: 105 grams Tumor Site: Lower area Tumor Size: 5 x 4 x 4.5 cm Tumor Characteristics: Solid and cystic with necrosis. Focality: Unifocal Adrenal gland: Not seen. Macroscopic Extent of Tumor Gerota's fascia: Intact Renal Sinus: Renal sinus involvement by tumor not identified Renal vein invasion: Absent Renal Capsule Grossly Intact: Yes. 
Microscopic features: Histologic Type: Nephroblastoma, regressive type. Necrosis: Present (99% of tumor). Nephrogenic Rests: Absent. Anaplasia: Absent Margins: Margins uninvolved by tumor. Renal Sinus: Not involved. Regional Lymph Nodes: Four lymph nodes, free of tumor (0/4) Adrenal Gland: Free of tumor.
Comment(s): Most of the tumor shows chemotherapy-induced changes (necrosis, fibromyxoid and sclerotic stroma with hemorrhage and hemosiderin-laden macrophages). Only rare microscopic foci of epithelial elements within muscular stroma and rare blastemal cells are seen.

Diagnosis: Right kidney, radical nephrectomy: Nephroblastoma, regressive type.  

  • horseshoe kidney is the most common type of congenital fusion anomaly of kidneys in children. 
  • Wilms tumor is the most common intra-abdominal solid mass lesion in children.
  • Wilms tumor has increased incidence in horseshoe kidneys.
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Case information

rID: 56748
Published: 24th Nov 2017
Last edited: 14th Aug 2019
Inclusion in quiz mode: Included
Institution: King Hussein Cancer Center

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