Management of incidentally discovered appendiceal neuroendocrine tumors after an appendicectomy

Abstract

Appendiceal neuroendocrine tumors (aNETs) are an uncommon neoplasm that is relatively indolent in most cases. They are typically diagnosed in younger patients than other neuroendocrine tumors and are often an incidental finding after an appendectomy. Although there are numerous clinical practice guidelines on management of aNETs, there is continues to be a dearth of evidence on optimal treatment. Management of these tumors is stratified according to risk of locoregional and distant metastasis. However, there is a lack of consensus regarding tumors that measure 1-2 cm. In these cases, some histopathological features such as size, tumor grade, presence of lymphovascular invasion, or mesoappendix infiltration must also be considered. Computed tomography or magnetic resonance imaging scans are recommended for evaluating the presence of additional disease, except in the case of tumors smaller than 1 cm without additional risk factors. Somatostatin receptor scintigraphy or positron emission tomography with computed tomography should be considered in cases with suspected residual or distant disease. The main point of controversy is the indication for performing a completion right hemicolectomy after an initial appendectomy, based on the risk of lymph node metastases. The main factor considered is tumor size and 2 cm is the most common threshold for indicating a colectomy. Other factors such as mesoappendix infiltration, lymphovascular invasion, or tumor grade may also be considered. On the other hand, potential complications, and decreased quality of life after a hemicolectomy as well as the lack of evidence on benefits in terms of survival must be taken into consideration. In this review, we present data regarding the current indications, outcomes, and benefits of a colectomy.

A Case of Familial Appendiceal Neuroendocrine Tumor

“…For tumors larger than 2 cm or with mesoappendix infiltration or vascular or lymphatic vessel invasion, somatostatin receptor scintigraphy or PET scan using gallium 68–labeled somatostatin analogs should be considered with a right hemicolectomy to be performed afterward. 11…”

“…10 Management of aNET is dictated by the size of the tumor, mesoappendix invasion, margins, and lymphatic involvement. 11 After a complete resection of an incidentally diagnosed welldifferentiated aNET measuring less than 1 cm, no further diagnostic testing or intervention is required. When aNET is between 1 and 2 cm, an abdominal CT scan or magnetic resonance imaging to evaluate the presence of lymphatic involvement or distant metastasis is indicated.…”

“…After progression in somatostatin analogs, the patient with positive imaging may receive peptide receptor radionuclide therapy. 11…”

“…For tumors larger than 2 cm or with mesoappendix infiltration or vascular or lymphatic vessel invasion, somatostatin receptor scintigraphy or PET scan using gallium 68-labeled somatostatin analogs should be considered with a right hemicolectomy to be performed afterward. 11 For tumors between 1 and 2 cm, after diagnosis of aNET, controversy arises when deciding whether an appendectomy is sufficient or the patient will have better outcomes with right hemicolectomy. The main purpose to complete a right hemicolectomy is to complete the regional lymph node dissection that was found to be involved in 6%-9% of cases.…”

“…In cases of more advanced disease, patients with either tumor located at the base of the appendix, infiltration of the cecum, positive surgical resection margins, mesoappendix invasion, metastatically infiltrated mesoappendiceal lymph node, or the presence of undifferentiated or low differentiated cells or presence of goblet cells are advised to have further surgical intervention involving a right hemicolectomy. 11 A large meta-analysis showed a survival rate ranging from 95.6% reaching 100% in a 10-year follow-up period. 11 No specific recommendations on follow-up after resection of an aNET and no adjuvant therapy are needed after complete resection of a well-differentiated midgut NET.…”