Table 1.

WHO classifications of GEP-NENs

WHO 1980	WHO 2000	WHO 2010
I. Carcinoid	Well-differentiated endocrine tumor Well-differentiated endocrine carcinoma Poorly differentiated endocrine carcinoma/small-cell carcinoma	Neuroendocrine tumors  NET G1 (Grade 1)  NET G2 (Grade 2) Neuroendocrine carcinoma  NEC G3 (Grade 3):   Large-cell NEC   small-cell NEC
II. Mucocarcinoid III. Mixed carcinoid-adenocarcinoma forms	Mixed exocrine–endocrine carcinoma	Mixed adeno-neuroendocrine carcinoma (MANEC)
IV. Pseudotumor lesions	Tumor-like lesions	Hyperplastic and preneoplastic lesions