Presence of iron in colorectal adenomas and adenocarcinomas

Iron overload reportedly increases the risk of colorectal neoplasms, but the distribution of tissue iron in a colorectal neoplasm remains controversial. In this study, we attempted to determine the significance of tissue iron in colorectal adenomas and adenocarcinomas.

This study investigated 138 colorectal neoplasms (54 adenocarcinomas, 25 adenomas with high-grade dysplasia, and 59 adenomas with low-grade dysplasia) that were removed by surgical or endoscopic resection in Konkuk University Hospital between August 2005 and August 2006. Adjacent normal colon tissues and colorectal neoplasms were stained with Perls' Prussian blue to reveal ferric compounds.

Positive Perls' staining was evident in 35.2% (19/54) of the adenocarcinomas and 22.6% (19/84) of the adenomas, and in only 2.2% (3/138) of the samples of adjacent normal colon tissue (p<0.001). Iron appears to reside exclusively in the stroma and outside the gland, rather than in the epithelial cells. Iron expression was strong in larger (p=0.004) and pedunculated (p<0.001) adenomas, and in all types of adenocarcinomas regardless of their size, shape, and location.

The frequent presence of iron in the stroma of large adenomas, pedunculated adenomas, and adenocarcinomas indicates that iron deposition is a secondary phenomenon to intralesional hemorrhage rather than a consequence of epithelial-cell carcinogenesis.