When does a negative tissue sample constrain mosaic distribution?
questionA negative result outside the initially positive tissue is informative only if sampling and assay sensitivity make dropout unlikely. For the postzygotic ACTB variants and TP53 mosaicism sources, what evidence supports calling a finding tissue-restricted? Relevant distinctions are whether compartments were sampled independently, whether the same variant-specific detection limit applied in each compartment, and whether cell or lineage composition could dilute the signal. Orthogonal confirmation in the original specimen verifies the finding but does not establish its distribution.
