Background: Germline TP53 mutations are associated with Li-Fraumeni syndrome (LFS). However, approximately 20% of commercial laboratory multigene panel test (MGPT)-detected pathogenic TP53 variants represent aberrant clonal expansion (ACE), rather than a germline finding, and are often detected in individuals that lack classic features of LFS. Clonal hematopoiesis (CH) is a form of ACE, and in the absence of an abnormal hemogram is termed Clonal hematopoiesis of indeterminate potential (CHIP). CHIP is often associated with a pathogenic variant (PV) in hematopoietic pathway gene(s) at a variant allele frequency (VAF) less than expected for a heterozygous germline finding. The prevalence increases with age and exposure to chemotherapy. The presence of a skewed VAF is usually noted in a comment on a genetic test result, however, clinicians without genetic training often lack understanding of the comment and need strategies to discern the difference between germline findings, CHIP, and post-zygotic mosaicism. Our studies illuminate possible strategies for discernment for clinicians. Methods: Among 113 cases with MGPT-detected TP53 PVs, enrolled in the Clinical Cancer Genomics Community Research Network registry, we obtained additional tissues, family history and complete blood count (CBC) reports on 42 cases. DNA extracted from formalin fixed paraffin embedded (FFPE) tumor/normal tissues, blood, saliva, eyebrow plucks, was analyzed using a previously validated custom myeloid and CH gene (n = 79) amplicon-based QIAseq panel. PVs with VAF > 2% were included in analyses. Results: Germline status was confirmed for 6 cases (one with a CH PV), post-zygotic mosaicism was supported for 5 cases and 2 were indeterminant. 12 had results supporting ACE/CH, with additional CH-associated PV(s) identified in 5/12 (41%); n = 2 of each TET2, ATM, TP53; and increasing VAF over time for the driver TP53 PV was noted in 2. Of these 2 one was identified to have a hematopoietic malignancy identified through analysis of the CBCs and bone marrow biopsy in parallel with the increasing VAF. Additional results are pending for 7 cases. Conclusions: With the use of our multi-tissue NGS strategy, serial sampling of suspected ACE/CH cases, family history and CBC analyses we were able to discern the status of most TP53 genetic findings. This work has direct translational impact, refining risk estimation and improving the clinical care of patients with TP53 PVs, while avoiding unnecessary LFS-related care and enabling appropriate care for those with ACE.