Fatal Pulmonary Tumor Thrombotic Microangiopathy Associated With Disseminated Carcinomatosis of the Bone Marrow From Occult Gastric Cancer: An Autopsy-Confirmed Case.

Pulmonary tumor thrombotic microangiopathy (PTTM) and disseminated carcinomatosis of the bone marrow (DCBM) are rare but life‑threatening metastatic complications of advanced malignancies, particularly gastric adenocarcinoma, and often present with hematological abnormalities such as disseminated intravascular coagulation and microangiopathic hemolytic anemia, making early recognition difficult. An 87-year-old woman was admitted with nausea and loss of appetite, and imaging revealed bilateral chronic subdural hematomas, pleural effusions, and multiple small pulmonary nodules. Laboratory tests showed anemia, thrombocytopenia, markedly elevated coagulation markers, and increased tumor markers, while bone marrow biopsy confirmed DCBM with poorly differentiated adenocarcinoma. Before the primary tumor site could be identified, the patient developed rapidly worsening hypoxia and died despite steroid pulse therapy. Autopsy revealed a type 4 gastric adenocarcinoma with extensive lymphatic invasion and pulmonary tumor microemboli with fibrocellular intimal proliferation, confirming PTTM as the cause of respiratory failure. This case illustrates the simultaneous occurrence of DCBM and PTTM due to advanced gastric cancer and underscores the importance of considering these conditions in patients with unexplained cytopenias, coagulation abnormalities, or acute respiratory decline when gastric adenocarcinoma is suspected.