Collision of primary adenocarcinoma of the lung with metastatic adenocarcinoma in the colon: A case report

Introduction. Collision tumors occur when two tumors of different histological origin develop simultaneously at the same site, such as sarcoma and carcinoma combinations, carcinoma and lymphoma combinations, or others. Notably, collision tumors are less common in the lungs compared to other organs. Case report. A 65-year-old woman with a history of surgically and chemotherapeutically treated colon adenocarcinoma underwent a regular chest radiographic check-up at a hospital. A follow-up examination and computed tomography revealed two oval lesions in the right lung lobe, later confirmed through histopathological and immunohistochemical analysis. One lesion was identified as primary lung adenocarcinoma, while the other was a metastasis of colon adenocarcinoma. Diagnosis of lesions with distinct histological origins relies on determining the expression of specific markers. Lung adenocarcinoma typically expresses TTF-1 in 90% of cases, while metastases originating from colonic adenocarcinoma often exhibit CDX2 marker expression in 99% of cases. Conclusion. Several theories attempt to explain the formation of collision tumors. The first hypothesis suggests that their origin lacks a specific pattern or predictable cause. The second hypothesis proposes that environmental changes, influenced by carcinogenic stimuli, promote the simultaneous growth of two tumors. Lastly, it is hypothesized that tumors modify the organ's microenvironment, increasing the likelihood of nearby metastatic colonization. To ensure effective treatment of collision tumors, accurate and precise diagnosis, along with a comprehensive understanding of the tumor's characteristics, is crucial.