WHO 2000 WHO 2010 1. Well-differentiated endocrine 1. NET G1 tumour (WDET)   2. Well-differentiated endocrine 2. NET G2a carcinoma (WDEC)   3. Poorly-differentiated endocrine 3. NEC G3 (large cell or small cell) carcinoma (PDEC)   4. Mixed exocrine-endocrine 4. Mixed adenoneuroendocrine carcinoma carcinoma (MEEC) (MANEC) 5. Tumour-like lesions (TLL) 5. Hyperplastic and preneoplastic lesions G, grade; NEC, neuroendocrine carcinoma; NET, neuroendocrine tumour. a G2 NET may include WDET or WDEC of the WHO 2000 classification.

Table 1: Definitions for NETs of the digestive system according to WHO classifications.