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Paediatric Pathology Online

Pathology of Paediatric Renal Tumours

Dr Sampurna Roy MD   

 

                                                                                                                      

 

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).

Mesoblastic Nephroma -  i) classical   ii) cellular

Wilms’ tumour (nephroblastoma) i) without anaplasia ii) with anaplasia

   - Nephrogenic rests ;

   - Cystic partially differentiated nephroblastoma ;

Clear cell sarcoma of kidney (CCSK) ;

Malignant rhabdoid tumour of kidney;

Nephrogenic adenofibroma;

Metanephric adenoma;

Others:

Ossifying renal tumour of infancy;Renal medullary cell carcinoma; Renal cell carcinoma ; Angiomyolipoma; Peripheral Neuroectodermal Tumours (PNET) .

 

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.

Angiomyolipoma is easy to diagnose in the context of tuberous sclerosis, but may cause problems in small biopsies when it occurs in isolation. Extrarenal Angiomyolipoma

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.

Peripheral Neuroectodermal Tumours (PNET ) of the kidney has only been recognized recently, with only a few cases described in the literature. Extraskeletal Ewing's Sarcoma / PNET.

Peripheral Neuroectodermal Tumours (PNET) is rarely an organ based tumour, but presents more often in soft tissue (Example: paraspinal, chest wall).

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.

Differential Diagnosis:

Although classical renal tumours of childhood pose few diagnostic difficulties, differential diagnosis may prove difficult in atypical cases.

Useful clues which are helpful in reaching the correct diagnosis  include age, and unique histological and clinical features of certain tumours.

Many tumours occur in well defined age groups.

Mesoblastic Nephroma is the most common tumour in a neonatal period, but it never occurs after 3 years of age.

Similarly, rhabdoid tumour of kidney is usually diagnosed in the first 3 years of life, rarely up to 5 years, and is virtually never seen in older age groups.

In contrast, anaplastic Wilms’ tumour has never been diagnosed in the first 6 months of life, is extremely uncommon up to first 2 years of life, but is far more common after the age of 5 years.

Clear cell sarcoma of kidney is extremely rare under 6 months of age, its peak incidence is in the second to third year.

A Wilms' tumour is the only typical renal tumor of childhood which may be bilateral (in about 5% of cases) and multicentric.

Other unique histological features of Wilms' tumour are the presence of nephrogenic rests, skeletal muscle, and fat.

Genuine neoplastic tubules are characteristic, but also seen in metanephric tumours.

Also, only Wilms’ tumour may be familial or associated with syndromes such as hemihypertrophy, Beckwith-Wiedemann syndrome (BWS), WAGR (Wilms tumour, Aniridia, Genitourinary abnormalities, mental Retardation) and Denys-Drash (DD) [glomerulopathy, male genital abnormalities] syndrome.

 

Further reading:

Pediatric renal masses: Wilms tumor and beyond.

An approach to renal masses in pediatrics.

Wilms' tumor and other pediatric renal masses.

Renal neoplasms of childhood.

Pediatric renal tumors.

Drug resistance in renal tumors of childhood.

Classification of malignant pediatric renal tumors by gene expression.

Cytopathology of uncommon malignant renal neoplasms in the pediatric age group.

Fine needle aspiration cytology characteristics of renal tumors in children.

 

 

 

Dr Sampurna Roy  MD

Consultant  Histopathologist (Kolkata - India)


 

 

 

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