Subtotal Gastrectomy for Atypical Carcinoid of Stomach– A Rare Tumour

Subtotal Gastrectomy for Atypical Carcinoid of Stomach– A Rare Tumour 1. Lt Col SM Shahadat Hossain, MBBS, MCPS, FCPS (Surg) FCPS (Thoracic Surg), Classified Surgical Specialist & Thoracic Surgeon, CMH, Dhaka; 2. Brig Gen Md Mahbubur Rahman, MBBS, FCPS, Chief Surgeon, CMH, Dhaka; 3. Maj Md Rayhan Mahmud, MBBS, Graded Surgical Specialist, AFMI, Dhaka; 4. Dr Farhana Israt Jahan, MBBS, FCPS (Gynae & Obs), Officers on Special Duty, DG Health, Mohakhali, Dhaka. Fig-1: Endoscopic image of poorly differentiated gastric carcinoid tumours showing large, irregular friable mass CT scan of abdomen: Circumferential wall thickening is noted in the antral part of stomach with luminal narrowing, leading to proximal dilatation of stomach. Post contrast scan revealed enhancement of the lesion. Fig-2: Computed tomography scan of abdomen with oral contrast demonstrates evidence of enhancing irregular thickening in the antrum The patient underwent subtotal gastrectomy and gastrojejunostomy. Histopathological examination of gastric mass was suggestive of atypical carcinoid tumour of the stomach. He received three cycle chemotherapy post operatively. He had been followed up at six months interval. Fig-3: Histology slides photomicrographs of a poorly differentiated gastric carcinoid tumour stained with H & E chromogranin A and synaptophysin JAFMC Bangladesh. Vol 12, No 2 (December) 2016 146 147 JAFMC Bangladesh. Vol 12, No 2 (December) 2016 Discussion Gastrointestinal carcinoids arise from neoplastic proliferation of enterochromaffin cells or Kulchitsky cell. Incidence of carcinoid is estimated at 0.8-2.1 new cases per 100,000 people per year and majority are sporadic in nature. In 2000, World Health Organization revised the classification of GEP-NET, abandoning the term carcinoid in favour of NET. The age of presentation ranges from 4th to 8th decade. The exact aetiology of carcinoid tumourogenesis is not known. Only a few risk factors for gastrointestinal (GI) carcinoid tumours are known e.g. genetic syndromes, Tuberous sclerosis, Von Hippel-Lindau disease, Multiple endocrine neoplasia type-I, Neurofibromatosis type-I. Carcinoid tumours are more common among African Americans than whites slightly, more common in women than men. Carcinoid tumours are classified, depending on the site of origin, as foregut (lung, thymus, stomach, duodenum) or midgut (distal ileum, proximal colon) or hindgut (distal colon, rectum). Fig-4: Sites of carcinoid tumour In 28.5% cases it occurs in small intestine, 28% in bronchial system of the lungs,14% in rectum, 5-7% in colon, 5% in appendix, 4% in stomach, 1% in pancreas, 1% in liver and 8% in others. World Health Organisation histological classification of Gastrointestinal endocrine tumours. (a) Well-differentiated endocrine tumour, Carcinoid: An epithelial tumour of usually monomorphous endocrine cells showing mild or no atypia and growing in the form of solid nests, trabeculae or pseudoglandulae, restricted to the mucosa or submucosa. (b) Well-differentiated endocrine carcinoma, Malignant carcinoid: A malignant epithelial tumour of endocrine cells showing moderate atypia and growing in the form of solid nests, trabeculae or larger less well-defined cellular aggregates, which deeply invades the gut wall (muscularis propria or beyond) or shows metastases to regional lymph nodes or liver. (c) Poorly differentiated endocrine carcinoma, Small cell carcinoma: A malignant epithelial tumour composed of highly atypical, small to intermediate-sized tumour cells growing in the form of large, ill-defined aggregates, often with necrosis and prominent angioinvasion and/or perineural invasion. The biological and clinical characteristics of the tumours vary considerably. Most of the gastric carcinoids show no evidence of endocrine function. They may synthesize and secret serotonin (5-HT) which is metabolized to 5-hydroxyindoleacetic acid (5-HIAA). Other hormones secreted are ACTH, histamine, dopamine, substance P, prostaglandins, kallikrein and tachykinins. This patient presentation was associated with antral carcinoma stomach and histopathologically revealed atypical carcinoid tumour. He did not have any feature of carcinoid syndrome. The differential diagnoses of the syndrome include inflammatory bowel disease, gut neoplasia, diverticular disease and irritable bowel syndrome. Endoscopy and endosonography are common diagnostic tools. CT and MRI are required to assess the presence of metastases and plan of surgery. Measurement of urinary 5-HIAA levels (73% sensitivity and 100% specificity) is used for confirming the diagnosis and monitoring patients with metastatic disease. Other markers help in diagnosis are chromogranin -A, neuron-specific enolase, synaptophysin and CDX-2. Somatostatin receptor Scintigraphy, Gallium-68 receptor PET are newer modalities for diagnosis. Surgery is the only curative therapy for NETs if performed before metastasis. Surgical options are endoscopic mucosal resection, partial gastrectomy and total gastrectomy.