Table 1: Comparison of classification systems of Head and Neck NENs between WHO 2005 and WHO 2017 Blue Books.
| Salivary glands 2005 | - | - | Small cell NEC | Large cell NEC | |
| Salivary glands 2017 | - | - | Small cell NEC (under poorly differentiated carcinoma) | Large cell NEC (under poorly differentiated carcinoma) | |
| Nasal cavity- Paranasal sinuses 2005 | Typical carcinoid | Atypical carcinoid | Small cell carcinoma neuroendocrine type | ||
| Nasal cavity- Paranasal sinuses and Skull base 2017 | - | - | Small cell NEC | Large cell NEC | |
| Larynx 2005 | Typical carcinoid | Atypical carcinoid | Small cell carcinoma neuroendocrine type | Combined small cell – non small cell carcinoma | Paraganglioma |
| Hypopharynx, larynx trachea and para- pharyngeal space 2017 | Well differentiated NEC | Moderately differentiated NEC | Poorly differentiated NEC, small cell neuroendocrine carcinoma | Poorly differentiated large cell neuroendocrine carcinoma |