Synchronous Colorectal Carcinoma: Three Cases Report and Literature Review

Background: Multiple primary colorectal cancers (MPCC) includes synchronous colorectal carcinoma (SC) and metachronous colorectal carcinoma (MC), which are defined as multiple malignant colorectal tumors that occur simultaneously or heterochrony. Comparing to isolate colorectal cancer, the incidence of SC is still rare. At present, there are few literatures describing the cases and reviews of SC. Case presentation: Here, we present three cases of SC. The first patient was admitted to our hospital because of a 5-month history of abdominal pain associated with difficult defecation. PET-CT revealed that a mass lesion of the splenic flexure of colon and another mass in sigmoid. Colonoscopy demonstrated double lesions in splenic flexure and sigmoid. Then we performed traditional open subtotal colon resection. Postoperative pathology confirmed that there are malignant characteristics of the double lesions. Another patient was suffered from with dizziness and fatigue for more than 2 years. Abdominal contrast-enhanced CT shows irregular thickening of the ascending colon wall and colonoscopy reveals that there is a tumor in rectum and many polyps in sigmoid. Then we underwent radical resection of rectal cancer and right colon cancer in a laparoscopic operation. Postoperative pathology confirmed moderately differentiated adenocarcinoma of the rectum and ascending colon. The third patient had hematochezia for 1 year. Both rectal magnetic resonance imaging (MRI) and colonoscopy showed that there are two lesions in the rectum, and conventional laparoscopic APR surgery was performed. Postoperative pathology confirmed malignant tumors in the rectum respectively. The mini review summed up the main points about prevalence, clinical manifestation, diagnosis, pathological, treatment and molecular mechanism features of SC based on current literature, which probably has significant distinctions with solitary tumors. Conclusions: Compared with isolated colorectal cancer, SC usually has a low stage，grade and incidence, but the age, sex and location is still a controversial issue. Colonoscopy and surgery are considered to be the best diagnosis and treatment method for SC. At present, serrated adenoma, hyperplastic polyp, ulcerative colitis and Crohn's disease are considered to be closely related to SC. MSI and gene mutation are two molecular mechanisms that lead to SC.