Pulmonary Tumor Thrombotic Microangiopathy Secondary to Extramammary Paget's Disease: An Autopsy Case Report

ABSTRACT Pulmonary tumor thrombotic microangiopathy (PTTM) is a rare and frequently fatal complication of metastatic malignancy, characterized by rapidly progressive dyspnea and severe pulmonary hypertension. This report describes the case of a 75‐year‐old man who was scheduled to receive systemic chemotherapy following imaging studies that revealed right inguinal lymph node metastasis and multiple osseous metastases associated with extramammary Paget's disease (EMPD). Before the initiation of treatment, the patient developed acute‐onset, rapidly worsening dyspnea. In the context of known metastatic malignancy, severe pulmonary hypertension, and nonspecific computed tomography findings, a clinical diagnosis of PTTM was made. Oral therapy with imatinib was initiated; however, the patient's respiratory condition deteriorated, and he died 5 days after the onset of respiratory symptoms. Postmortem examination confirmed the diagnosis, revealing microscopic tumor emboli within multiple pulmonary vessels, accompanied by fibrin thrombi. PTTM originating from cutaneous malignancy is exceedingly rare. This case highlights an uncommon presentation of PTTM secondary to EMPD and includes a review of relevant literature.