Metastatic Colon Cancer: A Rare Presentation of Parotid Gland Metastasis: 2845

Colorectal cancer is the third most common type of cancer in the United States and has the potential of metastasizing to nearly any organ in the body. We present a rare case of metastatic colon cancer to the parotid gland. A 64-year-old male presented with a history of adnocarcinoma of the esophagus and colon. PET-CT showed no metastatic disease. The esophageal disease was reported T3N0 and the transverse colon disease T3N1. Ideally the patient would have pursued neoadjuvant chemoradiation followed by surgery, but he was not a candidate hence systemic chemoradiation was not performed. He underwent a right hemicolectomy followed by a short course of palliative radiation therapy to his chest. 6months later he developed a new left parotid mass. Biopsy of the left parotid gland, showed a poorly differentiated adenocarcinoma. Immunohistochemistry determined that this was likely from lower GI origin making metastatic disease from his colon cancer the most likely source. Unfortunately, he remains a poor candidate for systemic chemotherapy due to his advance age and poor performance status, hence arrangements were made to initiate radiation therapy in palliation. Colorectal cancer is a common and potentially lethal disease. Estimates range as high as 134,490 new cases of colon cancer are diagnosed annually in the US. Approximately 49,190 Americans are expected to die of colon cancer each year which has decreased significantly since 1990 at a rate of approximately 3% per year presumably due to better screening methods. Approximately 20% of patients in the US have distant metastatic disease at the time of presentation. The most common metastatic sites are the regional lymph nodes, liver, lungs, and peritoneum. Parotid gland involvement by adenocarcinoma of the colon is extremely rare. Metastatic involvement of the parotid gland may arise from lymphatic spread, hematogenous dissemination, or contiguous involvement. Contiguous extension is common with malignancies of the supporting tissues in the parotid region, whereas the parotid gland is unusual as the focus of a distant primary tumor. Most metastases to the parotid gland arise from primary tumors in the head and neck region, usually being either melanomas or squamous cell carcinomas. Colorectal carcinoma has the potential to metastasize to almost any organ of the body. Although rare, metastatic adenocarcinoma from the colon should be included in the differential diagnosis of lesions of the parotid gland.