Collision metastasis of prostatic and colonic adenocarcinoma: report of 2 cases.

Collision metastases of carcinomas in lymph nodes are rare. Carcinoma metastasizing to lymph nodes containing malignant lymphoma has also been reported. The literature contains 3 cases of collision metastasis of prostatic and urothelial carcinoma. To our knowledge, we report the first 2 cases of collision metastasis of prostatic and colonic adenocarcinoma, one involving a mesenteric lymph node and the other involving a perirectal lymph node, both from resections for colonic adenocarcinoma in patients with known metastatic prostatic carcinoma.