An Interesting Case of Chimera: InconclusiveBRCA Analysis due to Two Distinct GeneticProfiles in a Single Patient

Background: Our case study proposes an explanation for the inconclusive BRCA testing we received on one of our patients. The BRCA analysis was inconclusive due to the specimen being chimeric, or having two distinct genetic profiles. We propose the Vanishing Twin theory as the most probable explanation. We have found no other reported cases of chimera linked to Vanishing Twin Syndrome in the literature. Methods: In this case report, we have described the presentation and operative course of a single patient of our Breast Center in 2017 to help define the setting of our unique BRCA analysis result. Findings: We have also done an extensive literature search in an attempt to understand the implications of the BRCA analysis result in a chimeric patient. However, our search was not satisfied by any direct evidence. We can only conclude that the Vanishing Twin theory is the most likely explanation of chimera in this single patient. Conclusions: We were unable to find any direct explanation for our results but we do propose this as an interesting case, as chimera is rare. In the future, it would be interesting to research whether chimera is, in fact, linked to Vanishing Twin syndrome, and whether these patients have any distinct protection from or predilection for certain disease processes.