Karcinoomid

Karcinoomid, known in English as carcinoid tumors, are a subset of neuroendocrine tumors that originate from neuroendocrine cells, most notably enterochromaffin cells in the gastrointestinal tract, pancreas, and, less commonly, the lungs. They tend to grow slowly and may be asymptomatic for years. Most arise in the gastroentero-pancreatic system, with the small intestine (especially the ileum), appendix, and rectum being common sites; bronchopulmonary carcinoids account for a smaller share.

Pathophysiology and clinical features: Many carcinoids secrete serotonin and other vasoactive peptides. When tumor burden is hepatic or when metastases permit serotonin to enter the systemic circulation, carcinoid syndrome can develop, characterized by episodic flushing, diarrhea, abdominal cramps, and bronchospasm. Prolonged exposure to serotonin can lead to carcinoid heart disease, typically affecting the right-sided heart valves.

Diagnosis and grading: Evaluation starts with clinical suspicion and biochemical testing, including elevated 5-hydroxyindoleacetic acid (5-HIAA) in urine and elevated chromogranin A. Imaging includes CT or MRI and functional imaging with somatostatin receptor PET (Ga-68 DOTATATE). Tumor grade is determined histologically; well-differentiated neuroendocrine tumors are graded by Ki-67 index and mitotic rate (G1, G2, G3), with higher grades indicating greater proliferative activity.

Treatment and management: Localized tumors are treated with surgical resection. Advanced disease may benefit from liver-directed therapies. Systemic therapy includes somatostatin analogs (e.g., octreotide, lanreotide) to control symptoms and slow growth, and peptide receptor radionuclide therapy (PRRT) with Lu-177 DOTATATE for somatostatin receptor–positive tumors. Targeted therapies such as everolimus or sunitinib are used in selected pancreatic NETs, and cytotoxic chemotherapy is reserved for high-grade neuroendocrine carcinomas and certain tumor subtypes.

Prognosis and terminology: Prognosis depends on tumor location, stage, and grade, with localized, well-differentiated tumors having a better outlook than metastatic disease. The term karcinoomid reflects historical usage; in current practice these tumors are categorized as neuroendocrine tumors.