Stage IV Lung Adenocarcinoma Discovered After Cancer Cells Were Found in a Stroke Clot

What happened, in summary

A 76-year-old man was hospitalized with a severe stroke causing left-sided weakness, visual loss, and speech difficulty. He underwent mechanical thrombectomy to reopen the blocked right middle cerebral artery. Brain imaging showed the stroke but no brain metastases at that time.

Unexpectedly, examination of the removed clot found malignant epithelial cells. Further testing supported a pulmonary adenocarcinoma, and chest CT then revealed a large left lower-lobe mass with mediastinal lymph-node involvement and invasion of a pulmonary vein. The cancer was Stage IV. Testing showed very high PD-L1 expression at 90%, a TP53 mutation, and no actionable driver alteration.

Pembrolizumab was started as first-line immunotherapy. Although his neurologic function initially improved enough for discharge with mild residual deficits, new frontal brain metastases appeared and his overall condition worsened rapidly. He died 51 days after the index stroke. The case illustrates an unusual presentation in which the stroke clot itself provided the first clue to an otherwise occult lung cancer.