Professional Practices and Diagnostic Issues in Neuroendocrine Tumour Pathology: Results of a Prospective One-Year Survey among French Pathologists (the PRONET Study).

Introduction: Many changes have recently occurred in the practice of neuroendocrine tumour (NET) pathology. We therefore aimed to evaluate how pathologists have adapted their daily practice to the most recent international guidelines for diagnostic and prognostic evaluation.

Procedures: A 12-month prospective study (PRONET) was carried out among French pathologists between August 2010 and July 2011. Data were collected using an anonymous electronic case report form.

Observations: Five hundred laboratories were invited, 149 accepted to participate, 80 were active and 59 provided eligible cases. A total of 1,340 cases were collected. The primary tumour was gastroenteropancreatic in 58.1% of cases and thoracic in 18.1%; it was from another site in 9.7%; 12.3% of cases were metastases of unknown origin. Pathological diagnosis was made from the examination of surgical samples in 58.1% of cases, biopsy specimens in 33.5%, endoscopic resections in 3.1% and cytological preparations in 4.2%. For the demonstration of the neuroendocrine nature of the tumour, chromogranin A and synaptophysin were tested in, respectively, 97.1 and 82.8% of cases. The differentiation status was definitely provided in 95.7% of cases. Mitotic count was attempted in 80.1% of cases and Ki67 index in 80.7%. In gastroenteropancreatic (GEP)-NETs, histological grading was available in 95.9% of the cases. WHO classification was available or feasible in 94.1% of GEP-NETs and 93.8% of thoracic NETs. TNM staging was performed according to International Union against Cancer in 74.8% of GEP-NETs and according to European Neuroendocrine Tumour Society in 55.6%.

Conclusions: The PRONET study shows that the current recommendations and diagnostic procedures are satisfactorily respected by most pathologists in daily practice.