Histological Diagnosis and Frequency of Primary Endocrine Tumors (ETs) and Neuroendocrine Tumors (NETs) According to WHO Classification

The new WHO classification provides the foun-dation for tumor diagnosis, patient treatment and tools for clinico-epidemiological research. This study was conducted to determine the fre-quency and update the histological aspects of different endocrine and neuroenodocrine tumors for clinical significance and to minimize unclas-sified lesions. Materials and Methods: Five hundred biopsies were analyzed in the Pathology Department of King Edward Medical University from 1st June 2004 to 31st December 2005. Tumors were diag-nosed with light microscopy using the new WHO classification. Results: Following 500 biopsies, 145 (29%) Endo-crine(ET) and Neuroendocrine Tumors (NET) were found; majority of the former, ET, n=112 (77.2%), were in the thyroid, of which 84 (75%) were follicular adenomas and 28 (25%) were carcinomas, of the 28 carcinomas, the frequencies were: papillary carcinoma (PC) 21 (75%); anaplastic(AC) 4 (14.28%); follicular(FC) 2 (7.14%); and medullary (MC) 1 (3.57%). Of the 145, 33 (22.8%) were neuroendocrine tumors (NET), with the following types and frequencies: adrenal 13 (39.5%); pituitary 10 (30.5%); pancreatic 4 (12%); parathyroid 3(9%); appendix 1 (3%); and rectum 1 (3%). One NET detected in the thyroid region was a well-differentiated neuroendocrine carcinoma (WDNEC). Among adrenal NETs, of 13 only 2 (14.4%) were malignant and diagnosed as a cortical and a neuroblastoma respectively, while all others were benign NETS, as follows: cortical adenoma 2 (15.38%); pheochromocytoma 7 (53.8%) and 1 (7.69%) ganglio neuroblastoma, and ganglioneuroma each respectively. All pituitary, parathyroid and pancreatic NETS were benign in nature. NETS of the appendix and rectum were WDNETS, while that of the lung was a WDNEC. Findings of this study confirm that the WHO classification provides uniform, simple, repro-ducible and practical criteria for diagnosis of ETs and NETS.