Immunohistochemical differences between mucinous and microglandular adenocarcinomas of the endometrium and benign endocervical epithelium.

Mucinous and microglandular adenocarcinomas of the endometrium (MUC-AD and MIGL-AD, respectively) are uncommon types of endometrial cancer. When present in endometrial biopsy or curettage, these tumors may display a unique microglandular architectural pattern mimicking benign microglandular hyperplasia (MGH) of the endocervix. We compared the immunoprofile of MUC-AD and MIGL-AD with that of MGH and benign endocervical glands to identify the markers that would reliably separate these malignancies from benign endocervical tissue. A total of 10 MIGL-AD and 30 MUC-AD cases were collected for the study. Fifteen consecutive cases of benign endocervical glands and MGH were used as a control group. All cases were stained for vimentin, p16, Ki-67, BCL-2, survivin, CD10, and CD34. p16 was the only marker that showed a significantly different staining pattern between the benign and malignant cases, whereas the staining for vimentin, Ki-67, BCL-2, and survivin demonstrated marked overlaps. All but 1 MUC-AD and MIGL-AD cases were positive for p16, whereas none of the cases of benign mucinous endocervical epithelium and MGH showed p16 positivity. Furthermore, the stromal cells of endocervix demonstrated weak to moderate positivity for CD10 and strong positivity for CD34, whereas endometrial tumors showed a reverse pattern, with strong stromal positivity for CD10 and either no, or only weak, staining for CD34. In conclusion, epithelial p16 and stromal CD10/CD34 immunostaining can be useful in distinguishing MUC-AD and MIGL-AD from benign endocervical epithelium in endometrial sampling.