Colon cancer metastasis to mediastinal lymph nodes without liver or lung involvement: A case report.

Colon cancer is the second most common type of cancer in females and the third in males, worldwide. The most common sites of colon cancer metastasis are the regional lymph nodes, liver, lung, bone and brain. In this study, an extremely rare case of colon adenocarcinoma with extensive metastasis to the mediastinal lymph nodes without any other organ involvement is presented. A 44-year-old Caucasian male presented with abdominal pain, a change in bowel habits, melena and weight loss. Colonoscopy revealed a large friable, ulcerated, circumferential mass in the ascending colon. Biopsies were consistent with the diagnosis of invasive moderately differentiated adenocarcinoma. Subsequently, right colon resection was performed, and pathological analysis revealed moderately differentiated adenocarcinoma of the right colon with extensive regional lymph node involvement. Computed tomography (CT) scans of the chest, abdomen and pelvis were performed preoperatively as part of routine staging for colon cancer. No liver or lung pathology was identified; however, multiple pathologically enlarged mediastinal lymph nodes were observed. Endoscopic ultrasound with fine needle aspiration of the largest mediastinal lymph node, which measured 5.2×3.5 cm on CT scans, was performed. The pathology was again consistent with the diagnosis of metastatic colorectal primary adenocarcinoma. At present, no optimum treatment has been identified for metastatic colon cancer to the mediastinal lymph nodes. The patient in the current case received chemotherapy with folinic acid, fluorouracil and oxaliplatin (FOLFOX), as well as with bevacizumab. Initial follow-up CT scans of the chest revealed a positive response to treatment. Physicians, in particular, radiologists, must consider the mediastinum during the first evaluation and further follow-up of patients with colorectal carcinoma even in the absence of metastasis.