Small Bowel Neoplasms

Small bowel cancer encompasses a series of malignant lesions that may be identified throughout the small intestine (SI). The small bowel lies between the stomach and the large intestine (LI/colon). It comprises three different sections, the duodenum, jejunum, and ileum, to the level of the ileocecal valve, which provides the terminal transition point between the SI and the LI. While both benign and malignant lesions can be identified throughout the SI, the overall incidence of small bowel neoplasms is extremely low compared to lesions noted in other portions of the gastrointestinal tract. This article will focus on the overall characteristics, diagnostics, treatment, and prognosis of malignant lesions. The majority of these lesions cause multiple nonspecific symptoms, which often leads to delay in diagnosis and therefore delay in early intervention with available treatment strategies. Common clinical features include abdominal pain, anorexia, gastrointestinal bleeding, and weight loss. More advanced processes can present with perforation, small bowel obstruction, or obstructive jaundice. Diagnosis can be variable based on the location of the lesion under investigation and generally consists of laboratory studies, radiographic imaging, and endoscopic evaluation. Malignant lesions overall include lymphomas, neuroendocrine tumors (carcinoids), adenocarcinomas, and stromal tumors. Adenomas are the most prevalent benign tumors of the small intestine. However, other non-malignant pathologies, ranging from 30 to 50% of SI tumoral lesions, with dominant vascular, lipidic, and lymphatic components might involve the small intestine and include fibromas and lipomas, hemangiomas, lymphangiomas, and neurofibromas. It has been estimated that small intestine tumors might be diagnosed in almost 0.3% of autopsies. As the mentioned incidence rate is significantly lower than any surgical procedural rate to address small intestine tumors, one might conclude the significant fraction of asymptomatic patients with SI tumoral involvement. Many of these lesions arise from the duodenum and might be recorded solely as a part of surveillance esophagogastroduodenoscopy. Despite the uncommon diagnosis of primary small bowel cancers, almost 10,000 new patients were diagnosed recently in the United States. Moreover, small intestine adenocarcinoma, carcinoid tumor, and lymphoma have been considered the most common small intestine malignancies in the order of decrease. An updated classification of small-intestine tumors identified previously classified tumors as leiomyomas and leiomyosarcoma as Gastrointestinal stromal tumors (GISTs). It recognized them as the most prevalent mesenchymal tumors involving the small intestine. Moreover, the small intestine might be involved in metastatic disease, specifically in patients with melanoma or with the local invasion from the adjacent involved organ.