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.