Histopathological analysis of a retrieved cerebral thrombus revealing occult lung adenocarcinoma: a case report

Background Cancer-associated stroke (CAS) is a heterogeneous entity in which hypercoagulability represents the most common mechanism, whereas direct tumour embolism is rare and likely under-recognised. Case presentation A 76-year-old white European man presented with acute left hemiplegia, hemianopsia and dysarthria (NIHSS 18). Non-contrast CT showed early ischaemic changes (ASPECTS 7), CT angiography demonstrated occlusion of the right middle cerebral artery, and CT perfusion revealed a favourable mismatch profile. Mechanical thrombectomy achieved partial recanalisation (TICI 2b). Histopathological examination of the retrieved thrombus revealed malignant epithelial cells. Immunohistochemical analysis was consistent with lung adenocarcinoma with high PD-L1 expression. Continuous cardiac monitoring and 72-h Holter-ECG showed no atrial fibrillation, and transthoracic echocardiography identified no major cardioembolic source. Laboratory testing showed only moderately elevated D-dimer levels. Subsequent chest CT identified a large necrotic mass in the left lung invading the pulmonary vein. Despite initiation of immunotherapy, the patient developed brain metastases and died 51 days after the index stroke. Conclusions Tumour embolism is a rare but clinically relevant mechanism of ischaemic stroke. It should be considered in patients with embolic stroke of undetermined source, even in the absence of markedly elevated D-dimer levels. Histopathological analysis of thrombectomy specimens may provide clinically relevant diagnostic information and facilitate early detection of occult malignancy in selected patients.