Gastric Carcinoids

+ General Considerations

Gastric carcinoids are tumors of the enterochromaffin system and are referred to as amine precursor uptake and decarboxylation tumors or APUDomas
Gastric carcinoids are functional and, in humans, are diagnosed by clinical presentation, measurement of urinary serotonin metabolites, provocative pentagastric testing, radionucleide scans, and CT
Carcinoids are locally invasive, and metastasize to regional lymph nodes, lungs, pleura, and peritoneum
Carcinoids usually occur in geriatric animals and gastric carcinoid has been reported in a 15-year-old cat

Clinical signs are caused by gastric outflow obstruction, altered motility, or chronic blood loss secondary to tumor necrosis and ulceration
Progressive vomiting is common and may contain fresh or digested blood
Weight loss may be caused by poor digestion, protein malnutrition, or cancer cachexia

Laboratory tests and survey radiographs are usually unrewarding
Microcytic hypochromic anemia is common with chronic blood loss and occult blood may be detected in feces
Increased liver enzymes may be seen with hepatic metastasis or obstruction of the common bile duct

Positive- or double-contrast radiographs: gastric tumors can appear as a mass effect, ulcer crater, delayed gastric emptying with poor motility, and delayed adherence of contrast material to an ulcerated tumor

Ultrasonographic findings include transmural thickening of the gastric wall with loss or altered layering (poor echogenic outer and inner lining with hyperechoic central zone)
Other findings include tumor location, ulceration, extension through gastric wall, and lymphadenopathy

Gastroscopy allows direct visualization and guided biopsy
Several biopsies should be performed as superficial ulceration, necrosis, and inflammation is common
Submucosal masses are difficult to biopsy and false-negative results are common

CT and MRI

Surgery is recommended for gastric carcinoids, but complicated by advanced stage at presentation, frequent metastasis, difficult access, and debilitated animal
Lymph node metastasis is variable and all abdominal lymph node should be evaluated for staging purposes
Curative resection should be attempted if disease is localized to the stomach
Surgical techniques: Billroth I or II or palliative bypass procedures
Billroth I or II provides immediate relief of gastric outflow obstruction and clinical improvement in early postoperative period
Billroth II (partial gastrectomy and gastrojejunostomy) or complete gastrectomy (with biliary by-pass) are very extensive surgeries with high morbidity and minimal survival advantage
Partial gastrectomy preferred in humans due to better nutritional status and quality of life and radical gastrectomy does not improve survival time
Palliative gastrojejunostomy for inoperable or metastatic lesions but associated with significant morbidity including anastomotic ulcers

No known effective chemotherapy agents for gastric carcinoids, consider somatostatin analogues

Prognosis depends on surgical excision, tumor type and grade, and presence of metastatic lesions
Prognosis is unknown for gastric carcinoids