Lynch syndrome with colon squamous cell carcinoma is rare. This article reports a case of Lynch syndrome with colon squamous cell carcinoma as the initial manifestation. The patient is a 68 year old male who sought medical attention due to right upper abdominal pain. During the surgery, it was found that the tumor extensively involved the abdominal cavity. Under the microscope, atypical tumor cells are arranged in nests, and immunohistochemistry detection shows that tumor cells P63, P40, and CK5/6 are diffusely positive, CDX2 is weakly positive, CK7, CK20, and Villin are all negative, and MSH2 expression is missing. Pathogenic mutations (c.2038C>T) were found in the MSH2 embryo line through second-generation sequencing. This article discusses the clinical and pathological characteristics of this rare tumor in conjunction with literature.