Tumors of the small intestine: epithelial/mesenchymal, neuroendocrine, lymphomas
Tumours of the small intestine are rare, usually single, and can be malignant or benign. Symptoms of all SI tumours are generic, stomach pain, nausea, weight loss, occasional rectal bleeding.
Malignant tumours
- Adenocarcinomas
- These develop from adenomas (precursor), mostly at the ampulla of the duodenum. Crohn’s and celiac are risk factors
- Intestinal Lymphoma
- Complication of celiac, and can occur in immunodeficiency syndromes
- Leiomyosarcoma
- Tumour arises from smooth muscle wall of the intestine, can also arise from benign leiomyoma
- Neuroendocrine
- Includes Carcinoid, Gastrin cell & Somatostatin cell tumours
H&E: low-grade neuroendocrine (carcinoid) tumour of the small intestine – normal villi and crypts at the top; below them, nests and islands of small, uniform tumour cells infiltrate the bowel wall.
Image: “Low-Grade Neuroendocrine ("Carcinoid") Tumor of the Small Intestine (37266217195)” by Ed Uthman from Houston, TX, USA, CC BY 2.0, via Wikimedia Commons.
Example: a patient with an ileal carcinoid that has spread to the liver develops carcinoid syndrome – flushing, diarrhoea, bronchospasm and fibrosis of the right-sided heart valves – because serotonin released by the liver metastases is no longer broken down in the liver.
Benign tumours
- Leiomyoma
- Adenomas
- Lipomas
- Hemangiomas
- Neurogenic tumours (most commonly neurofibroma)