Tumor-to-Tumor Metastasis in Synchronous Primary Kidney and Colon Tumors

Background: Synchronous tumors are defined as two or more distinct and malignant tumors excluding the possibility of one being a metastasis of the other. The development of tumor metastasis from another synchronous primary malignancy is rare. The incidence of synchronous neoplasms of the colon and kidney is rare. Renal cell carcinoma exhibits characteristic features making it suitable for harboring metastases. Case presentation: We report a unique case of a 49-year-old male with no previous history of cancer that was found to have synchronous rectal adenocarcinoma and left kidney renal cell carcinoma. Additionally, metastasis from colon adenocarcinoma to RCC was identified. Distinguishing double primary neoplasms and metastases in synchronous primary tumors has significant implications with respect to patient prognosis and recommendations for therapy.