Evaluation and Treatment of Appendiceal Carcinoid
Carcinoid tumors are the most common tumors of the appendix, accounting for more than half of all appendiceal malignancies. Carcinoid tumors arise from cells called subepithelial neuroendocrine cells in tissues throughout the body, and can be diagnosed in many locations throughout the gastrointestinal (GI) tract. They account for 5% of all carcinoid tumors identified in the GI tract and are more common in women than men. The mean age of patients at diagnosis is 49 years. Appendiceal carcinoid tumors are often incidentally discovered – they are found on routine pathology review in seven of every 1,000 appendectomy specimens. Approximately two-thirds of appendiceal carcinoid tumors arise in the tip of the appendix, where they are unlikely to cause symptoms of obstruction. Ten percent of appendiceal carcinoids occur in the base of the appendix, at the connection with the cecum, where they are more prone to obstruct the appendix and cause acute appendicitis.
Radiographic investigations for evaluation of appendiceal carcinoid
Most appendiceal carcinoid tumors are not specifically identified on preoperative imaging, but rather diagnosed incidentally on pathology review after appendectomy for presumed acute appendicitis. Occasionally, CT scans can diagnose these tumors pre-operatively.
Contrast-enhanced triple phase CT or MRI scanning can be utilized to assess the liver for metastatic disease once the diagnosis of carcinoid is suspected. Imaging based on interaction with the somatostatin receptor, such as octreotide scan or DOTATATE PET scan, can also be useful to detect extra-hepatic metastatic disease.
Management following a diagnosis of appendiceal carcinoid
Tumor size has been shown to be the best predictor of prognosis in patients diagnosed with appendiceal carcinoid tumors. The surgical management of appendiceal carcinoids depends largely on the size and location of the primary tumor. According to current guidelines, simple appendectomy is adequate for the treatment of small carcinoid tumors (< l cm). Indications for more extensive surgery have been shown to include tumor size >2 cm, lymphatic invasion, lymph node involvement, spread to the mesoappendix, tumor-positive resection margins, and cellular pleomorphism with a high mitotic index. Given that approximately one-third of patients with tumors exceeding 2 cm will present with or develop nodal and distant (systemic) metastases, most experts advocate a right hemicolectomy as the appropriate surgical treatment option for these patients. The management of tumors between 1 and 2 cm in size continues to be debated; however, a more aggressive treatment algorithm which includes right hemicolectomy is often employed, especially in younger patients. Additional prognostic factors (gender and depth of penetration of the tumor) may be utilized in choosing between appendectomy and hemicolectomy in these patients. If there is a suspicion for hepatic metastases or clinical carcinoid syndrome, measurement of 24 hour urinary serotonin metabolite 5-hydroxyindoleacetic acid (5-HIAA) levels is indicated.