Differences between right- and left-sided colon cancer in patient characteristics, cancer morphology and histology

Background and Aim: Recently, the clinical and biological differences between right‐ and left‐sided colon cancers have been widely debated. However, close analyses of these clinical differences, based on large‐scale studies, have been scarcely reported. Methods: A total of 3552 consecutive Japanese colorectal cancer cases were examined and the clinical differences between right‐ and left‐sided colon cancer cases were investigated. Results: The proportion of right‐sided colon cancer was relatively high in patients aged less than 40 years (33%) and more than 80 years (43%). The proportion of right‐sided colon cancer in patients aged 40–59 years was relatively low (male 22% and female 29%). In male patients the proportion increased in the 70‐79 years age group (30%), while in female patients the proportion increased in the 60‐69 years age group (39%). Right‐sided colon cancer was more likely to be detected at an advanced stage (T1 stage; left 22%, right 15%) (P < 0.01) with severe symptoms. Polypoid‐type early cancer was dominant in the left colon (left 59%; right 40%) (P < 0.01), while the proportion of flat‐type early cancer in the right colon was significantly higher than that in the left colon (left 25%; right 44%) (P < 0.01). Conclusions: Specific age distribution of right‐sided colon cancer was observed and the difference between male and female patients was highlighted. Other clinical features also differed between right‐ and left‐sided colon cancer, suggesting that different mechanisms may be at work during right and left colon carcinogenesis.