Rare germline chromosome 1 duplication identified in young male with colon cancer: a case report investigating causality

Background: The occurrence of colorectal cancer (CRC) is increasing among young adults, but the etiology is still largely unknown. In addition to germline monogenetic variants also polygenic risk scores (PRS) have been proven to correctly estimate the risk of CRC. Case Description: We present a 24-year-old male with disseminated colon cancer who carried a germline duplication on chromosome 1 spanning 200 kb and covering CD101, TTF2, MIR942, TRIM45, and parts of PTGFRN and VTCN1. The duplication was located in tandem. A similar duplication was previously reported in a family with CRC among two brothers aged 52 and 61 years old at diagnosis. Particularly, MIR942 was an interesting finding as it is involved in the regulation of the Wnt signaling pathway. Disruption of the Wnt pathway is known to cause CRC. However, in our case the duplication did not segregate with disease in the family. Calculation of a PRS in our patient found an average PRS for CRC. Conclusions: Our findings do not support that this duplication is a monogenetic cause of CRC, nor did a PRS point towards an increased risk in this 24-year-old male. Whether the duplication is a risk factor in combination with other genetic and non-genetic risk factors requires further studies.