Paediatric Pathology Online
Pathology of Paediatric Renal Tumours
Renal tumours of childhood are a very interesting group of tumours and recognition of their clinicopathological features and appropriate treatment represents a success story of paediatric oncology.
However, apart from Wilms' tumour, they are very rare and an average paediatric pathologist is likely to see very few in his/her professional career, making the correct diagnosis difficult.
Therefore, it is critical that these tumours are studied by a panel of pathologists who developed their expertise by studying a large number of cases in multicentre trials.
Renal tumours other than Wilms' tumours are infrequent in childhood.Wilms' tumours account for 6% to 7% of childhood cancer, whereas the remaining renal tumors account for less than 1%.
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The most common non-Wilms' tumors are clear cell sarcoma of the kidney, rhabdoid tumor of the kidney, renal cell carcinoma, mesoblastic nephroma, and multilocular cystic nephroma.
Collectively, these tumours account for less than 10% of the primary renal neoplasms in childhood.
The survival of Wilms’ tumour has increased from 5% to around 90%. This has in part been achieved by cooperation between pathologists that has led to the recognition of benign and malignant childhood renal tumours (mesoblastic nephroma, clear cell sarcoma, malignant rhabdoid tumour,nephrogenic adenofibroma etc).
Other renal tumours in children:
Many other renal tumours occur less commonly in children.
Renal cell carcinoma-like areas are sometimes seen in Wilms’ tumours, but pure renal cell carcinoma may arise in the context of von Hippel Lindau syndrome or sporadically. (von Hippel Lindau disease - ocular manifestation)
Renal medullary cell carcinoma is associated with sickle cell trait, and is an aggressive rumour of young adults.
Some cases are composed exclusively of epithelioid smooth muscle cells and may closely simulate renal cell carcinoma.
Positive reactions for HMB45, desmin and muscle specific actin helps in difficult cases.
However, it seems to have a predilection for the kidney where it affects older children than Wilms' tumour as well as adults.
The usual histological appearance is of nodules and sheets of monotonous small round cells and focal formation of rosettes.
Immunohistochemistry is positive for neuron specific enolase and CD99.
Published examples show t(11;22)(q24;q12) as in soft tissue PNETs.
The outlook is often poor with the tumours presenting at an advanced stage and showing a poor response to chemotherapy.
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