P53 expression in synchronous colorectal cancer.

OBJECTIVE We reviewed cases of primary colorectal adenocarcinoma to document synchronous colon and rectum adenocarcinoma (SCRC). METHODS In a retrospective setting, 764 cases underwent surgical resection for primary colorectal adenocarcinoma and referred to the Department of Surgical Pathology, Uludag University, Medical Faculty for diagnoses between 1997 and 2006, were reviewed. Tumor site, depth of invasion, coexistence of adenoma, distance between these multiple primary tumors, degree of p53 expression, and p53 expression pattern indicating polyclonal or monoclonal origins were noted in order to establish a possible effect on prognosis. RESULTS There were 28 cases with SCRC of colon and rectum. Nine cases were female, 19 cases were male (female to male ratio was 1:2). Most of the cases were within the 5th and the 6th decades. There were statistically significant relationships between p53 expression and differentiation status (p=0.001), and invasion depth (p=0.03). Forty of 62 colorectal carcinomas showed immunohistochemical positivity for p53. Six cases showed a discordant pattern of p53 mutation among individual lesions indicating polyclonal origin. CONCLUSION Synchronous colon and rectum adenocarcinoma is not rare. The incidence is 3.6% in our series. We believe that further studies with larger series are needed for p53 to prove useful in predicting prognosis of SCRCs and assessing the polyclonal origin of SCRC at a genetic level.