Synchronous primary sigmoid colon cancer and primary thyroid cancer followed by a malignant tumor of the kidney: Case report of multiple primary cancer and review of the literature.

Multiple primary cancer (MPC) is relatively rare. With the development of diagnostic and anti-cancer therapeutic techniques, the incidence of MPC is rising annually. However, the incidence of triple or quadruple cancers in a single patient remains low. In this report, the case of a 58-year-old male with triple malignant cancer is outlined. Synchronous sigmoid colon cancer and thyroid cancer were diagnosed in May 2015; on subsequent re-examination, metastasis to the liver and a malignant kidney tumor were also identified. The diagnosis was established via computed tomography (CT), Positron emission tomography-CT (PET-CT) and other laboratory examination results, including analysis of tumor markers and liver function, and was confirmed by pathological diagnosis. The patient underwent radical surgery and standardized chemotherapy. Through literature review, the definition, characteristics, classification, incidence, possible causes of and treatment strategies for MPC were more clearly understood. In addition, immunohistochemical staining of integrin αvβ6 was performed on patient tissue specimens, where integrin αvβ6 expression was confirmed in cancer of the colon, thyroid and liver, as a result of colonic metastasis. Therefore, the involvement of integrin αvβ6 in the malignant progression of MPC was hypothesized, which may aid the investigation of MPC etiology in the future.