Small Intestinal Neuroendocrine Tumour Incidentally Diagnosed Along with Large Mesenteric Lymph Node Metastasis: A Case Report

Small intestinal neuroendocrine tumours (NETs) are rare malignancies that occur in the small intestine. The incidence of small intestinal NETs has increased substantially in recent decades. Similar to that of general NETs, the diagnosis rate of small intestinal NETs is increasing continuously. Small intestinal NETs often metastasize to the lymph nodes, even when the lesions are small. Surgical resection of the primary tumour and associated mesenteric lymph nodes is recommended. We present a case of a NET in the ileum that was incidentally diagnosed along with large mesenteric lymph node metastasis. Abdominal computed tomography for examination of urinary frequency revealed an intra-abdominal mass, measuring 80 mm in diameter. The patient was intraoperatively diagnosed with an ileocaecal mesenteric mass, and ileocaecal resection with lymph node dissection was performed. The resected specimen incidentally showed a NET measuring 14 mm in diameter in the ileum, located 90 cm from the ileocaecal valve. The ileocaecal mesenteric mass was histopathologically diagnosed as lymph node metastasis of the NET. This case confirms the importance of making an immediate intraoperative pathological diagnosis and performing a thorough examination of small intestinal lesions when a large mesenteric tumour is suspected.