Gastric Carcinoma

A 62-year-old woman undergoes upper GI endoscopy for chronic epigastric pain and is found to have a 2 cm submucosal bulge in the gastric fundus with intact overlying mucosa. The lesion appears smooth and yellowish. What is the most appropriate confirmatory investigation to establish the diagnosis of gastric gastrointestinal stromal tumor (GIST)?

The histopathology slide shown above, taken from a gastric biopsy, demonstrates features most consistent with which of the following diagnoses?

A 58-year-old Indian male presents with progressive dysphagia, early satiety, and unintentional weight loss of 8 kg over 3 months. Upper endoscopy reveals a 4 cm ulcerated lesion in the gastric antrum with irregular borders. Biopsies confirm adenocarcinoma. CT chest and abdomen shows no distant metastases, but there is thickening of the gastric wall. What is the most appropriate next step in management?

A 62-year-old woman is found to have metastatic gastric adenocarcinoma with HER2 overexpression (IHC 3+, FISH-positive) involving the liver and peritoneum. She is deemed unfit for surgery. What is the drug of choice for first-line palliative chemotherapy in this HER2-positive metastatic gastric cancer?

A 58-year-old Indian man with a 10-year history of chronic epigastric pain and H. pylori infection presents with progressive dysphagia and weight loss. Endoscopy reveals a large ulcerated lesion in the antrum. What is the most common site of gastric carcinoma in this patient?