Continuing trends in the prevalence of right-sided lesions among colorectal carcinomas.

The shift of colorectal carcinoma location toward the proximal colon has been reported. This study documents that this statistically significant trend has continued through 1992. An increase in transverse and descending colon cancers is now apparent also. Only 59% of all large-bowel cancers occurred distal to the descending colon between 1978 and 1992. Both right-sided and distal large-bowel cancers have significantly decreased in size, yet the incidence and frequency of lymph node metastases have not changed over a 65-year interval (from 1928 to 1992). This constant proportion of lymph node metastases may suggest distinct biological subsets of cancers (lymph node avid vs lymph node avoidance). The progression from small size with fewer metastases to large size with more lymph node metastases occurs only in some of the smallest distal colorectal cancers.