KRAS and lymphangioma: Beyond detection of tumor mutations, CSF ctDNA may have utility in LM detection and monitoring: In a case series of two patients with lung cancer, CSF ctDNA analysis revealed mutations in a signaling pathway oncogene K-ras prior to radiographic and cytologic confirmation of LM.33 Though a small series, further validation may demonstrate that ctDNA may provide diagnosis in the setting of negative cytology and imaging findings or identify individuals at risk for developing LM.