Endoscopic resection could be a promising curative treatment for cases of early colorectal carcinoma (CRC). If we can identify predictive factors associated with cancer progression, we should be able to establish improved indications for appropriate treatment modality for early CRC. An essential subunit of mediator complex, Med1, interacts with several nuclear receptors and transcription factors to direct gene-specific transcription. We analyzed 98 lesions of early CRC confined to the mucosa (44 cases) and having submucosal invasion (54 cases) to evaluate correlations between immunohistochemical expression of Med1 and cancer progression. The expression of Med1 was detected in the nuclei with/without cytoplasms of both the normal and the tumor cells. Loss of Med1 immunoreactivity was significantly higher in carcinoma with submucosal invasion (9/54, 16.7%) than in intra-mucosal carcinoma (2/44, 4.5%) ( p