Focal Leptomeningeal Disease with Perivascular Invasion in EGFR-Mutant Non-Small-Cell Lung Cancer.

We report a previously undescribed pattern of brain metastases in patients with epidermal growth factor receptor-mutated non-small-cell lung cancer treated with tyrosine kinase inhibitors and radiation therapy. These highly distinct lesions appear to spread focally within the leptomeninges, with invasion along the perivascular spaces (FLIP). The survival of patients with FLIP was significantly better compared with patients with classic leptomeningeal disease (median survival, 21 versus 3 months; P = .003). It is unclear whether this pattern of growth is unique to epidermal growth factor receptor-mutated non-small-cell lung cancer.