Lung cancer is globally one of the leading causes of malignant tumor‐related mortality and ranks as having the highest incidence found in men and second in women. Osimertinib is a drug used to target lung cancer but its toxicity is not fully understood. Here we present a case of lung adenocarcinoma in a 78‐year‐old man that was treated and responded favorably with Osimertinib after the failure of other therapies. Unfortunately, the patient developed severe interstitial lung disease during the treatment procedure.

Pulmonary tumor thrombotic microangiopathy (PTTM) is a rare cancer-related complication characterized by intimal proliferation in the pulmonary small arteries with or without tumor emboli, which can be fatal due to progressive pulmonary hypertension (PH). And PTTM is hard to be confirmed during lifetime; hence, it is vital to pay more attention to high-risk PTTM, which may progress quickly.PTTM patients have an extremely poor prognosis. Here, we have reported a case of a patient with both hepatocellular carcinoma (HCC) and gastric signet-ring cell carcinoma who presented with dyspnea and died rapidly and was diagnosed with suspected PTTM. In addition, we have reviewed some related literature. This patient showed a poorer prognosis, with a survival time of only 3 days after oxygen supplementation (very poor compared to the average level of PTTM patients caused by gastric carcinoma only, which was 18 days according to our summary). Besides, respiratory discomfort is the main symptom of PTTM. Abnormal pulmonary imaging was reported with the appearance of septal thickening, ground-glass opacities, small nodules, pleural effusion, and a tree-in-bud pattern in PTTM patients. No effective therapeutic options have been established for PTTM. PTTM should be considered in patients with cancer who progress to rapid respiratory failure and PH, especially in patients with multiple tumors whose condition is more likely to deteriorate quickly.