The role of immunohistochemistry in diagnosing a synchronous colon tumor.

: Simultaneous presence of an epithelial and lymphoid tumor of the digestive tract is quite rarely met in literature. In this paper, we describe a case which presented such an association. Diagnosis was established by histological study, followed by immunohistochemistry. It is a synchronous colon tumor, associating a non-Hodgkin's lymphoma to a colon adenocarcinoma. The 57-year-old male patient has been clinically diagnosed with a tumor of the left abdominal quadrant and paraclinically (imaging and endoscopic) with colon neoplasm. Exploratory laparotomy revealed two tumors: one tumor of five centimeters in the sigmoid, with firm consistency, mobile on lower plans and the second tumor in the ceco-ascending colon, measuring about 7 cm, irregular, with firm consistency, mobile on lower plans, with lymph nodes extending to retroperitoneal space. The urinary bladder, kidneys, liver and stomach were of normal aspect. Subtotal colectomy was performed with latero-lateral ileo-sigmoid anastomosis. Microscopic examination revealed sigmoid tumor as G1 adenocarcinoma and cecal tumor as B-cell type lymphoma. Immunohistochemistry established the final diagnosis of cecal localization being a diffuse immunoblastic large B-cell non-Hodgkin's malignant lymphoma. The final diagnosis of this patient was actually a synchronous manifestation of a colon adenocarcinoma and non-Hodgkin's lymphoma. This association puts into question synchronous tumors etiopathogeny matter.