Sialosyl-Tn expression in normal and pathological conditions of human endometrium. An immunohistochemical study

To assess the clinico-prognostic relevance of the cell surface carbohydrate glycoprotein in normal and pathological conditions of human endometrium, Sialosyl-Tn (STn) antigen was immunohistochemically studied in normal (n = 10), hyperplastic (n = 18), and neoplastic (n = 60) endometrial lesions. There was no STn antigen reactivity in the proliferative endometrial slides, while weak staining was observed in all secretory endometria. STn expression was noted in 8/18 (44%) hyperplastic endometrial cases and in 40/60 (67%) endometrial carcinomas. Positive staining was observed throughout the cytoplasm of the glandular cancer cells, at the cell membranes, and in an intraluminar mucus. This antigen was mostly expressed heterogeneously as far as the distribution of positive cells is concerned. There was a statistically significant association between STn expression and the histological grading of cancer (p = 0.019). Advanced clinical stage (III-IV; p = 0.014) and infiltration of the myometrial wall (more than 1/2 of the myometrial wall; p = 0.004), but no STn immunoreactivity, were reported to be independent prognostic variables during follow-up. Our study shows that a) STn is not constantly expressed during the menstrual cycle, and is increased at the secretory phase of the cycle; b) Sialosyl-Tn reactivity decreases with the degree of tumor differentiation, but there was no relationship with other clinicopathological variables of cancer; c) this cell surface carbohydrate glycoprotein does not appear to predict the outcome of endometrial cancer patients.