Rapidly progressive miliary brain metastasis of lung cancer after EGFR tyrosine kinase inhibitor discontinuation: An autopsy report.

Miliary brain metastasis is a rare type of brain metastasis, in which carcinoma cells disseminate to numerous foci confined to Virchow-Robin/subpial spaces. Symptoms usually progress within several months, and magnetic resonance imaging (MRI) shows multiple small contrast-enhancing lesions. We report an autopsy case of a patient who rapidly deteriorated within a week due to miliary brain metastasis after epidermal growth factor receptor tyrosine kinase inhibitor (EGFR-TKI) discontinuation, without contrast-enhancing lesions on MRI. A 74-year-old woman was diagnosed with stage IV lung adenocarcinoma with EGFR L868R mutation 2 years before presentation. Gefitinib, an EGFR-TKI was started. After 7 months, multiple new punctate contrast-enhancing lesions in the cerebral cortex appeared. After switching to another EGFR-TKI, erlotinib, these lesions disappeared. One year later, erlotinib was discontinued because of disease progression in the lung and docetaxel was initiated. Sixteen days later, cognitive decline appeared which rapidly progressed to bedridden state in 4 days. MRI showed multiple cortical small fluid-attenuated inversion recovery high intensity lesions which lacked contrast enhancement. The patient exhibited a state of akinetic mutism within a few days, and died 52 days after the appearance of neurological symptoms. The rapid progression indicated disease flare after EGFR-TKI discontinuation. Autopsy revealed numerous foci of metastasis in the cerebral cortex, basal ganglia, thalamus, and cerebellum, in which cancer cells were mostly confined to the Virchow-Robin/subpial spaces. These pathological findings were compatible with previous reports of miliary brain metastasis. Recent reports suggest that early disseminated cancer cells can survive for a long time and even remain after chemotherapy in supportive niches, and Virchow-Robin spaces are the niches in the brain. Our case suggests that these cancer cells may rapidly proliferate as a withdrawal burst after discontinuation of molecular targeted drugs, and show pathological findings of miliary brain metastasis.