Pulmonary tumor thrombotic microangiopathy due to early gastric carcinoma in a patient with no antemortem findings suggestive of primary malignancy

Pulmonary tumor thrombotic microangiopathy (PTTM) is a rare and critical malignancy-related disease characterized by acute progressive pulmonary hypertension (PH). In most cases of PTTM, the cancer can be diagnosed in advance. Identification of the primary cancer is valuable for PTTM diagnosis. Here, we present the case of a patient with PTTM due to early gastric carcinoma in whom the diagnosis of malignant cancer was not revealed until macroscopic autopsy findings. This case highlights the importance of recognizing causative occult early gastric cancer leading to PTTM in cases of acute progressive PH.