Solitary pulmonary nodule: primary, metastatic, or both

The lung is the most common site for metastasis from colorectal cancer, which is among the most common neoplasms in developed countries. Simultaneous occurrence of pulmonary metastasis of colorectal origin and primary carcinoma has been reported. We describe the case of a 65-year-old man who underwent low anterior resection for colorectal adenocarcinoma in 2007. Follow-up computed tomography revealed a pulmonary nodule that was classified as metastatic. The patient was referred to our thoracic surgery department, where the nodule was resected. The pathology confirmed that the nodule was neoplastic, and histologic and immunohistochemical examination showed the presence of colorectal metastasis and lung adenocarcinoma. Evidence of metastasis was also found in 2 of the lymph nodes analyzed, 1 with features identical to the primary pulmonary adenocarcinoma, and 1 with features identical to the colorectal metastasis.