A 62-year-old woman with a 10-year history of chronic atrophic gastritis and intestinal metaplasia presents with persistent epigastric discomfort and anemia (Hb 8.5 g/dL). Upper endoscopy shows a 4 cm polypoid mass in the gastric body with areas of ulceration. Histopathology reveals well-to-moderately differentiated adenocarcinoma with glandular structures arranged in tubules and acini, invading the submucosa (T1b). Immunohistochemistry shows CDX2 positivity and intestinal-type mucins. Based on the histological and molecular features, which statement best characterizes the pathogenesis and prognosis of this tumor?