Complications of carcinoid syndrome: diagnosis and treatment

Neuroendocrine neoplasms have heterogeneous morphological features and varying clinical manifestations, which in turn influences their therapeutic approach. Histologically, based on cell morphology, they can be divided into neuroendocrine tumors and neuroendocrine carcinomas. Clinically, they are subdivided into functioning (in the presence of a specific tumor syndrome) and nonfunctioning (in cases where only general, nonspecific symptoms are observed). One of the most common clinical manifestations of functioning neuroendocrine tumors is carcinoid syndrome, caused by the tumor’s secretion of multiple hormonal amines and peptides, primarily serotonin. In most cases, these tumors are relatively indolent. However, as the disease slowly progresses, patients may experience delayed complications such as carcinoid heart disease, mesenteric fibrosis, malnutrition, and vitamin deficiencies. Carcinoid syndrome can also rapidly worsen to a life-threatening complication known as a carcinoid crisis. Given the multifaceted and insidious nature of carcinoid syndrome, effective treatment relies on the indispensable role of a multidisciplinary team consisting of gastroenterologists, endocrinologists, radiologists, oncologists, nuclear medicine physicians, surgeons, cardiologists, and nutritionists.