Prevalence and Clinical Implications of Mismatch Repair-Proficient Colorectal Cancer in Patients With Lynch Syndrome.

PURPOSE: Lynch syndrome (LS)-associated colorectal cancer (CRC) is characterized by mismatch repair-deficiency (MMR-D) and/or microsatellite instability (MSI). However, with increasing utilization of germline testing, MMR-proficient (MMR-P) and/or microsatellite stable (MSS) CRC has also been observed. We sought to characterize MMR-P/MSS CRC among patients with LS. METHODS: Patients with solid tumors with germline MMR pathogenic/likely pathogenic (P/LP) variants were identified on a prospective matched tumor-normal next-generation sequencing (NGS) protocol. CRCs were evaluated for MMR-D via immunohistochemical (IHC) staining and/or MSI via NGS. Clinical variables were correlated with MMR status using nonparametric tests. RESULTS: Among 17,617 patients with solid tumors, 1.4% (n = 242) had LS. A total of 36% (86 of 242) of patients with LS had at least one CRC that underwent NGS profiling, amounting to 99 pooled CRCs assessed. A total of 10% (10 of 99) of CRCs were MMR-P, with 100% concordance between MSS status and retained MMR protein staining. A total of 89% (8 of 9) of patients in the MMR-P group had MSH6 or PMS2 variants, compared with 30% (23 of 77) in the MMR-D group (P = .001). A total of 46% (6 of 13) of PMS2+ patients had MMR-P CRC. The median age of onset was 58 and 43 years for MMR-P and MMR-D CRC, respectively (P = .07). Despite the later median age of onset, 40% (4 of 10) of MMR-P CRCs were diagnosed <50. A total of 60% (6 of 10) of MMR-P CRCs were metastatic compared with 13% (12 of 89) of MMR-D CRCs (P = .002). A total of 33% (3 of 9) of patients with MMR-P CRC did not meet LS testing criteria. CONCLUSION: Patients with LS remained at risk for MMR-P CRC, which was more prevalent among patients with MSH6 and PMS2 variants. MMR-P CRC was later onset and more commonly metastatic compared with MMR-D CRC. Confirmation of tumor MMR/MSI status is critical for patient management and familial risk estimation.

Trans-counseling: A case series of transgender individuals at high risk for BRCA1 pathogenic variants.

Transgender individuals comprise a growing patient population in genetic counseling practice. The identification of a pathogenic variant in a cancer susceptibility gene may impact a transgender person's decisions regarding hormonal and/or surgical transition. Limited scientific literature exists on specific genetic counseling needs and medical management strategies for transgender individuals. In addition, most genetic counselors have had limited experience and training in conducting genetic counseling sessions with transgender patients. In this report, we describe three cases of transgender individuals who underwent genetic counseling and testing in our clinic. All were at ≥50% risk to carry a familial BRCA1 pathogenic variant. Case 1 is a 20-year-old transgender female initiating hormonal agents. Case 2 is a 19-year-old transgender male considering surgical decisions who has a BRCA1 pathogenic variant on both sides of the family. Case 3 is a 24-year-old transgender male who had previously undergone gender-affirming mastectomy (top surgery) and is taking androgen therapy. Unique aspects of genetic testing, psychosocial counseling, and medical management of transgender individuals have arisen in the course of their care. In this report, we discuss our experiences and practices of case preparation, case management, appropriate genetic testing, and medical management such as screening, surgical decisions, and coordination of care. There is a need for more research in this area and more transgender-specific training for genetic counselors.