Abstract
Immunoglobulin G4-related disease (IgG4RD) is a relatively new disease concept that is most common in Asia. It is a systemic chronic lymphoproliferative disease that is diagnosed by mass formation or thickened lesion, a high serum IgG4 level (≥135 mg/dL), and confirmation of lymphocytes and plasma cells by histopathological examination. The precise mechanism of this disease remains elusive; however, distinguishing IgG4RD from malignancy proves challenging due to its manifestation of swollen lymph nodes and retroperitoneal thickening and fibrosis. Malignancy is also 3.5 times more likely in cases with IgG4RD. In this study, we report two cases of colorectal cancer in patients with IgG4RD who underwent surgery. In both cases, excising the tumor from the retroperitoneal posed a challenge, and swollen lymph nodes were observed without evidence of cancer metastasis. We believe that these are very informative cases, and we report the cases with a literature review of IgG4RD.