A 58-year-old Indian man presents with a 4-month history of progressive dyspepsia, early satiety, and unintentional weight loss of 8 kg. He has a 20-year history of chronic atrophic gastritis. On examination, he is pale and has a palpable left supraclavicular lymph node. Upper endoscopy reveals a large ulcerated lesion in the gastric antrum. Biopsy shows adenocarcinoma with signet-ring cells. CT staging shows no distant metastases but regional lymph node involvement. What is the most likely histological type and its association with this patient's gastric pathology?