All studies performed MSI analysis except one(Xu et al. 2020), IHC to identify MMR deficiency of MLH1, MSH2, MSH6, and PMS2 and germline analysis to confirm the absence of a DNA MMR gen,(Bucksch et al. 2020; Overbeek et al. 2007; Pico et al. 2020b; Rodriguez-Soler et al. 2013; Win et al. 2015), with three studies confirming the absence of EPCAM germline mutations (Bucksch et al. 2020; Pico et al. 2020b; Xu et al. 2020). The gene discussed is PMS2; the disease is mismatch repair cancer syndrome 1.