Clinicopathological Correlation of Invasive Histological Features in Incidentally Detected Appendiceal Neuroendocrine Tumors (aNETs)

Aim: Appendiceal Neuroendocrine Tumors (aNETs) are rare and mostly detected incidentally patients operated on acute appendicitis. These are indolent tumors and mostly benign, however they carry risk of metastasis. This study aims to identify invasive histological features of aNET cases, that are correlated with aggressive behavior other than stage and grading parameters. Material and Methods: This retrospective study includes patient demographics, surgical margin status and pathological features of tumors. ANETs showing adenocarcinoma features, goblet cell features, and mixed features were not included in our study. Results: The mean age of cases with tumors is 41years (11-61 years). The mean tumor diameter was found to be 6.8 mm. Most of tumors were located in the distal appendix (55.5%). All of the tumors show invasive features. Four cases showed invasion to submucosa (pT₁), four cases to muscularis propria (pT₁), eight cases to subserosa (pT₃), and four cases to mesoappendix (pT₃). Follow-up information was available for only one case with Grade-2 features and MAI, no additional surgical treatment was required, and he has survived at 3-year follow-up with no metastasis. Conclusion: Even if it is grade 1stage 1 tumors, may exhibit invasive features with a risk of metastasis. Although LVI and PNI are not included in ANET staging, they are important factors affecting the course of the disease. The literature lacks consensus on the advisability of performing completion right hemicolectomy in patients exhibiting invasive histological features. We believe it prudent to maintain regular follow-up intervals for these individuals