Hello. When sequencing cancer sample, it is recommended to sequence normal paired sample to exclude germline variants. For solid cancer, blood is normally used as norrmal paired sample. But for blood cancer like leukemia, blood cannot be used as normal paired sample, so other solid tissue like skin fibroblast should be used, which needs biopsy. However, in clinical context, it is hard to implement painful biopsy procedure for every patients.
Because body fluids including urine and saliva are all originated from blood, I think they may contain cfDNA from blood or lekocytes itself. And buccal swap sample also contains lekucytes along with epithelial cell.
When I only sequenced blood cancer sample without normal paired sample, I sometimes encountered situations that identifed genes or variants are known to be both germline and somatic, which is very confusing especially when the variant allele frequency is around 50%.
Are there any good ways to easily obtain a normal paired sample in blood cancer patients?