EGFR and malignant tumor of meninges: However, the patient developed an acute exacerbation of cancerous meningitis, and analysis using cell-free DNA from the spinal fluid suggested meningeal dissemination mainly caused by EGFR exon 19 p. E746_A750del mutant clones, which might have contributed to the worsening of the cancerous meningitis on selpercatinib treatment.