Case report: Tumor collision in the colon, adenocarcinoma – lymphoma

INTRODUCTION: Tumor collision is the cohesion in a time of 2 tumors in the same space or organ but of different cell lineage. PRESENTATION OF CASE: 72-year-old patient with a history of black stools, involuntary weight loss and moderate protein-calorie malnutrition, asthenia, and adynamia; with endoscopic studies with the finding of esophageal candidiasis that leads to taking a rapid test for HIV (human immunodeficiency virus) which is positive; CT (computerized axial tomography) of the abdomen is performed, showing thickening of the cecum and distal ileum, as well as striation of fat in the same area, findings related to a primary neoformative process, for which it is decided to carry out a right hemicolectomy laparoscopically with pathology that reports ulcerated moderately differentiated adenocarcinoma that invades up to the muscle layer, associated with lymphoid proliferation with immunohistochemical findings consistent with lymphoplasmablastic lymphoma, this is probably linked to his diagnosis of HIV, configuring the diagnosis of tumor collision; extension studies with no findings of metastatic neoplastic disease. DISCUSSION: Tumor collision is a rare entity, which implies failure in the genomic control and replication sites of different cell lines, which, due to their lineage, have different regulatory processes, all this occurring at the same time in the same tissue. CONCLUSION: The casuistry for collision tumors is scarce; even in the reference centers for oncology, the treatment is challenging given the multiple variables to consider, the particularity of each case, and the scarce evidence on the subject.