Response to Immunotherapy in Adenocarcinoma Lung With Gastric Metastasis: A Rare Case Report and Review of Literature.

Worldwide lung cancer is the most common cause of cancer mortality. Most of the lung cancer patients present with advanced disease at the time of diagnosis, and in that case, the prognosis is poor even with treatment. The most common sites of metastases in non-small-cell lung cancer are the brain, bone, liver, and adrenal gland. Metastasis to the stomach is extremely rare, which carries with itself a more dismal prognosis. Here we are reporting a rare case of adenocarcinoma lung with metastasis to the stomach, which was initially a diagnostic dilemma. The patient survived for 30 months from the diagnosis of gastric metastasis by management predominantly with immunotherapy.