Aims
Gastric‐type endocervical adenocarcinoma (EA) is characterised by aggressive behaviour and pathogenesis independent of human papillomavirus infection. Because of its morphology and frequent mutation‐pattern expression of p53, gastric‐type EA may be confused with several types of endometrial carcinoma, particularly in biopsy and curettage specimens. HIK1083 and MUC6 are immunohistochemical markers used to support a diagnosis of gastric‐type EA; however, the rates of expression of these markers in endometrial tumours are largely unknown. We therefore aimed to assess the expression of HIK1083 and MUC6 in a cohort of different types of endometrial carcinoma.
Methods and results
Ninety‐one endometrial carcinomas (56 endometrioid, 16 clear cell, and 19 serous) from 91 patients treated with hysterectomy were included. A representative tumour block from each case was used for immunohistochemical staining with HIK1083 and MUC6. The percentage of stained cells (0–100%) and average staining intensity (weak, moderate, and strong) were recorded for both markers. None of 91 cases expressed HIK1083. In contrast, 66% (60/91) of cases showed at least focal expression of MUC6; importantly, 54 of 60 (90%) positive cases showed moderate or strong staining. Five of 60 (8%) cases showed MUC6 staining in ≥50% of tumour cells. Endometrioid tumours (49/56, 88%) were more likely to express MUC6 than cases of clear cell (1/16, 6%) or serous (10/19, 53%) carcinoma.
Discussion
Endometrial carcinoma often expresses MUC6. In contrast, HIK1083 is consistently negative, and thus, when positive, is a more reliable marker for distinguishing gastric‐type EA from some of its endometrial mimics.