The present study reports the case of a collision tumor consisting of follicular lymphoma (FL) and adenocarcinoma in the cecum of a 73-year-old man. To the best of our knowledge, the present study is the 11th case of a collision tumor consisting of colon adenocarcinoma and lymphoma to be reported in the literature, and the first case of cecum adenocarcinoma with low grade FL in the same segment of the cecum and the same regional lymph node to be reported. The present study reviewed the literature to determine treatment options for patients with collision tumors. The present patient was administered with adjuvant chemotherapy for T3N1M0 colon cancer following surgery, due to the dominance of colon adenocarcinoma in the collision tumor. Following the completion of treatment, progression of the untreated FL was observed. In the literature, patients with collision tumors are administered with chemotherapy for stage IV FL, and following the completion of treatment patients have presented with a recurrence of early stage colon adenocarcinoma. The recommended treatment for collision tumors is dependent on the dominant tumor; however, the treatment options for collision tumors in the literature appeared to exacerbate the other tumor. The characteristics of the tumors altered following chemotherapy, and immunological alterations in the tumors due to chemotherapy appear to have contributed to the exacerbation of the tumors. Therefore, patients with early-stage tumors should be considered at risk of recurrence of other malignancies, which are present in collision tumors.
Keywords: collision tumor; colon cancer; follicular lymphoma; immune system.