Appendiceal Carcinoid / Well Differentiated Neuroendocrine Neoplasm / Tumor
Grading / Staging
- Histopathologic features are predictive of behavior (based on WHO, Odze and AFIP, each are a bit different)
- Benign
- Non-functioning
- Well differentiated
- ≤2 cm in greatest dimension
- Confined to appendiceal wall
- No involvement of mesoappendix
- No vascular invasion
- Uncertain malignant behavior
- As for benign, but with:
- >2 cm in greatest dimension and/or
- Vascular invasion
- Low grade malignant
- Non-functioning and well differentiated, with:
- Invasion of mesoappendix and/or
- Metastasis
- OR, functioning and well differentiated
- Any size and extent
- WHO 2010 also recommends the following grading scheme
- Mitotic counts based on 50 hpf
- Ki67 % based on 500-2000 cells
- If discrepant, use higher grade
- Scale proposed by European Neuroendocrine Society (ENETS)
- Carcinoids / neuroendocrine tumors may be G1 or G2
- G3 is definitional for high grade neuroendocrine carcinoma
- Progression from G1/2 to G3 is quite rare
- G3 appears to be a separate process
- Rindi G, Klöppel G, Couvelard A, Komminoth P, Körner M, Lopes JM, McNicol AM, Nilsson O, Perren A, Scarpa A, Scoazec JY, Wiedenmann B. TNM staging of midgut and hindgut (neuro) endocrine tumors: a consensus proposal including a grading system. Virchows Arch. 2007 Oct;451(4):757-62.
- Rindi G, Klöppel G, Alhman H, Caplin M, Couvelard A, de Herder WW, Erikssson B, Falchetti A, Falconi M, Komminoth P, Körner M, Lopes JM, McNicol AM, Nilsson O, Perren A, Scarpa A, Scoazec JY, Wiedenmann B; and all other Frascati Consensus Conference participants; European Neuroendocrine Tumor Society (ENETS). TNM staging of foregut (neuro)endocrine tumors: a consensus proposal including a grading system. Virchows Arch. 2006 Oct;449(4):395-401.
- Other features described above should also be reported
Proposed grading scale based on proliferation
Grade Mitotic count per 10 hpf % of cells Ki67+ G1 <2 ≤2 G2 2-20 3-20 G3 >20 >20 Grading/Staging References
- High grade / poorly differentiated neuroendocrine carcinoma is covered separately
- Staging
- AJCC TNM 7th edition now includes carcinoids of the appendix
- Key elements in staging are size (1, 2, 4 cm) and extension to cecum or ileum
