Clear cell adenocarcinoma of the colon: a case report and review of literature.

A primary clear cell adenocarcinoma of the colon is a rare oncologic entity. We herein report a case of such a tumor of the sigmoid colon in a 71-year-old woman who was successfully treated by an endoscopic polypectomy in our hospital. We also reviewed the published reports regarding cases of primary clear cell tumors in the colon.

Cytokeratin 7/20 and mucin core protein expression in ulcerative colitis-associated colorectal neoplasms.

Different histogenetic pathways have been suggested between ulcerative colitis (UC)-associated neoplasia and sporadic colorectal neoplasia. Little is known about the cytokeratin (CK) and mucin expression in UC-associated neoplasms. To clarify the characteristics of UC-associated colorectal carcinogenesis, we examined the immunohistochemical expression of CK7, CK20, MUC2, MUC5AC and MUC6 in 90 colorectal neoplasms, including 22 UC-associated adenocarcinomas (colitic cancer; CC), ten high-grade dysplasias (HGD) in UC, nine low-grade dysplasias (LGD) in UC, 24 sporadic tubular adenomas (TA) and 25 adenocarcinomas (AC). CK7 was positive in most of UC-associated neoplasms: 59% of CC cases, 80% of HGD and 89% of LGD, respectively, whereas, in non-UC associated neoplasia, 21% of TA and 12% of AC. The frequency of MUC6 expression in UC-associated neoplasia was 32% in CC, 30% in HGD and 44% in LGD, respectively, whereas, in non-UC associated neoplasia, 4.2% in TA and 0% in AC. MUC5AC expression in UC-associated neoplasia was detectable in 73% of CC, 90% of HGD and 89% of LGD, respectively; in non-UC associated neoplasia 67% in AC and 20% in TA. There were obvious differences in the expression of CK7 and MUC6 between UC-associated neoplasms and sporadic tumors. The incidence of MUC5AC expression in UC-associated neoplasms was also higher than sporadic tumors. These results suggest that gastric-type mucins play an important role in the initial step of CC-tumorigenesis, and CK7 and gastric-type mucins may be useful in the differential diagnosis between UC-associated neoplasms and sporadic ones.

Expression of cytokeratins 7 and 20 in serrated adenoma and related diseases.

The entity of serrated adenoma of the colorectum was first proposed in 1990, and it was characterized as epithelial neoplasia combining the architectural features of a hyperplastic polyp with the cytological features of an adenoma. Over the past few years, various clinicopathological studies on serrated adenoma have been reported, but its histogenesis remains unclear. Recently the existence of a "serrated neoplasia pathway" leading to malignancy, which is different from the so-called adenoma-carcinoma sequence, has been discussed. Yao et al. reported that hyperplastic polyps and serrated adenomas share a common cell lineage with gastric differentiation. To clarify the existence of the serrated neoplasia pathway, we performed immunohistochemical staining of cytokeratin 7 (CK7) and cytokeratin 20 (CK20), which are commonly used to determine the primary site of a metastatic lesion, and we examined the pattern of CK7/CK20 expression in various colorectal lesions including 44 serrated adenomas, 25 hyperplastic polyps, 20 traditional adenomas, and 48 carcinomas. An obvious difference existed in the pattern of CK7/CK20 expression between the serrated lesions (hyperplastic polyps and serrated adenomas) and others. The majority of serrated adenomas and hyperplastic polyps presented a CK7+/CK20+ pattern, whereas most conventional adenomas and adenocarcinomas expressed CK7-/CK20+. Adenocarcinoma developing in serrated adenoma also presented a CK7+/CK20+ pattern. There are several reports that CK7 is a possible marker of transient dedifferentiation in the gastric carcinogenesis process. Taken together with the present results, a distinct pathway of colorectal carcinogenesis must exist, which is different from the adenoma-carcinoma sequence. CK7 is a possible marker for the serrated neoplasia pathway of colorectal carcinogenesis.