Clinicopathological study of CD71/transferrin receptor 1 expression in colorectal tubular adenocarcinoma, tubular adenoma, and carcinoma in adenoma

CD71/transferrin receptor 1, a crucial type Ⅱ transmembrane glycoprotein, plays a vital role in regulating iron uptake and cell proliferation, and it is commonly found in various cancer cells. This study aimed to assess CD71 expression through immunohistochemistry in colorectal tubular adenoma, tubular adenocarcinoma, and carcinoma in adenoma, with the objective of determining the usefulness of CD71 immunohistochemistry in diagnosing colorectal cancer histopathologically. Subjects and Methods: The study included 28 colorectal tubular adenomas and 34 tubular adenocarcinomas obtained through endoscopic resection. Among the tubular adenocarcinomas, 16 （47％） were categorized as intra-adenoma carcinomas, and the adenoma and adenocarcinoma sections were evaluated separately. CD71 expression was evaluated across five grades: Grade 0 indicated no staining, Grade 1 denoted positive staining limited to the cellular membrane, Grade 2 represented weak and focal cytoplasmic positivity, Grade 3 indicated diffuse cytoplasmic positivity in portion of the tumor, and Grade 4 indicated intense and diffuse cytoplasmic positivity throughout the tumor. Statistical analysis involved the χ-square test and Fisher exact test for independence to compare differences between groups. Results: CD71 expression in adenoma was Grades 0, 1, 2, and 3 in 12, 13, 2, and 1 cases, respectively, with the majority falling into Grade 0-1 （n＝25） and no Grade 4 cases observed. Conversely, CD71 expression in adenocarcinoma was Grades 1, 2, 3, and 4 in 6, 6, 9, and 13 cases, respectively, with diffuse positivity being predominant and no Grade 0 cases identified. Among the 16 cases of carcinoma in adenoma, the adenoma portion exhibited low CD71 expression （Grades 0, 1, or 2） in all instances, whereas 10 of these cases showed elevated CD71 expression （Grades 3 or 4） in the adenocarcinoma portion. Conclusions: CD71/transferrin receptor 1 expression levels were notably lower in colorectal tubular adenomas compared to tubular adenocarcinomas. Moreover, CD71 demonstrated differential expression patterns between the adenoma and adenocarcinoma portions of carcinoma in adenoma originating from the same tumor clone, indicating that CD71 immunohistochemistry might serve as an additional tool in the histopathological diagnosis of colorectal tumors.