Management of incidentally discovered appendiceal neuroendocrine tumors after an appendicectomy

Table 1 TNM staging for appendiceal neuroendocrine tumor according to European Neuroendocrine Tumor Society and American Joint Committee on Cancer classification

	ENETS	AJCC
T0	No evidence of primary tumor	No evidence of primary tumor
T1	Tumor ≤ 1 cm with infiltration of submucosa and muscularis propia
T1a		Tumor ≤ 1 cm
T1b		Tumor 1-2 cm
T2	Tumor ≤ 2 cm with infiltration of the submucosa, muscularis propia and/or minimal (≤ 3 mm) infiltration of the subserosa and/or mesoappendix	Tumor 2-4 cm or with extension into the cecum
T3	Tumor > 2 cm and/or extensive (> 3 mm) infiltration of the subserosa and/or mesoappendix	Tumor > 4 cm or with extension into the ileum
T4	Tumor with infiltration of the peritoneum and/or other neighboring organs	Tumor with perforation of the peritoneum or invasion of other adjacent structures
N0	No regional lymph node metastasis	No regional lymph node metastasis
N1	Locorregional lymph node metastasis	Locorregional lymph node metastasis
M0	No distant metastasis	No distant metastasis
M1	Distant metastasis	Distant metastasis

ENETS: European Neuroendocrine Tumor Society; AJCC: American Joint Committee on Cancer.

Table 2 Summary of published data on appendiceal neuroendocrine tumor recurrence and survival

Author (Yr)	n	Recurrence rate	Specific disease survival rate	Reported follow-up
Tsikitis et al[38], 2012	982	-	95.6%	5-yr rate
Volante et al[17], 2013	138	-	97.1%	86.5 mo (1 - 267)
Mosquera et al[39], 2017	418	-	95.7%	5-yr rate
Sarchekeh et al[40], 2017	118	-	97.5%	10-yr rate
Pawa et al[41], 2017	215	0	99.05%	10-yr rate
Alexandraki et al[32], 2020	136	2.2%	100%	10-yr rate
Brighi et al[5], 2020	435	0%	98.5%	Median follow-up not provided, but at least 20% longer than 10 yr
Alabraba et al[1], 2021	102	1%	99%	6.2 yr (0.8-27.8)
Holmager et al[28], 2021	335	0%	100%	66 mo (1-250)

Table 3 Follow-up recommendations according to European Neuroendocrine Tumor Society and North American Neuroendocrine Tumor Society

Tumor characteristics	Surgery	Follow-up
Size < 1 cm	Appendectomy	No
Any size	Hemicolectomy (no lymph node involvement)	No (consider follow-up if tumor size > 2 cm)
Size 1-2 cm with poor prognostic factors	Appendectomy	History and physical examination every three to six months for the first year and then every six to 12 months
Any size	Hemicolectomy (lymph node involvement)	Consider tumor markers and abdominal imaging tests