Pathology of Primitive Neuroectodermal Tumour of the Pancreas

Dr Sampurna Roy MD            June 2016

 

Primitive neuroectodermal tumor (PNET - Small round blue cell tumour with evidence of neuroectodermal  differentiation ) of the pancreas is an extremely rare tumour that usually occurs in children or young adults (mean age 18 years - age range between 6 to 25 years).

The tumour accounts for 1% of all sarcomas.

The tumour usually occurs in soft tissue or bone of children/young adults.

Peripheral primitive neuroectodermal tumours are characterized by chromosomal translocation t(11;22)(q24;q12) in almost 90% cases.

At all sites, 5 year survival is 50%

Gross features:  Tumour is usually noted in the head of the pancreas (range between 3.0 to 9.0 cm in diameter).

Microscopic features:  Sheets and lobules of small round cells with scant cytoplasm. There is prominent nuclear molding and prominent mitotic activity.

The tumour often infiltrate into peripancreatic soft tissue.

Tumour necrosis may be present.

Usually there are no rosettes.

Immunohistochemistry: The tumour stains positively with CD99, cytokeratin, neuroendocrine markers (chromogranin, synaptophysin, NSE) and is negative with desmin.

Visit: PNET of the soft tissue

Differential diagnosis: 

Small cell carcinoma: Higher mitotic rate;numerous karyorrhectic bodies, focal glandular differentiation ;   ; usually elderly population.  t(11;22)

Pancreatoblastoma: Usually age 10 or less, acinar formations, squamoid corpuscles.   t(11;22).

Neoplasms of the Endocrine Tumours : Usually adults, no molding, negative for neuroendocrine markers, slow growing tumours.

Neuroblastoma: Younger patients, produce catecholamines. t(11;22).

Lymphoblastic lymphoma (CD99+ but TdT+ also),

Rhabdomyosarcoma :

Metastatic PNET to pancreas: PNET of the soft tissue

Intraabdominal desmoplastic small round cell tumour : Dense fibrous stroma, strong desmin staining, different t(11;22) than PNET.

PNETs should be included in the differential diagnosis of poorly differentiated small round cell tumors of the pancreas.

They should not be confused with pancreatic endocrine tumors, which also demonstrate dual epithelial and neuroendocrine differentiation by immunohistochemistry.

 

Further reading

Peripheral primitive neuroectodermal tumors arising in the pancreas: the first case report in Asia and a review of the 14 total reported cases in the world.

Huge primitive neuroectodermal tumor of the pancreas: report of a case and review of the literature.

Primitive neuroectodermal tumor of the pancreas.

[Primitive neuroectodermal tumor of pancreas].

[Diagnosis and treatment of primitive neuroectodermal tumors of pancreas].

Primitive neuroectodermal tumor of the pancreas. A case report of an extremely rare tumor.

Primitive neuroectodermal tumor of the pancreas. An extremely rare tumor. Case report and review of the literature.

 

 

 

 

Dr Sampurna Roy  MD

Consultant  Histopathologist (Kolkata - India)

 


 

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