Advanced cancer with situs inversus totalis associated with KIF3 complex deficiency: Report of two cases

Situs inversus totalis (SIT) is a relatively rare congenital anomaly, occurring at an incidence of 1 in 10 000–50 000 live births. Although there are some case reports of SIT with the presence of cancer, there are few reports on the relationship between SIT and cancer. However, the recent phylogenetic investigations of this condition suggest that this may be linked to the development and progression of cancer on the molecular level. The key elements are one of the intracellular motor proteins, the KIF3 complex, and the cell-adhesion factors N-cadherin and β-catenin. We herein present the cases of advanced gastric cancer and lung cancer with SIT, and review the relationship between SIT and the development and progression of cancer.