Expression Patterns of Cytokeratins (CK7, CK20, CK19, CK AE1/AE3) in Atypical Endometrial Hyperplasia Coexisting with Endometrial Cancer

Few studies have evaluated cytokeratin's (CK) staining patterns in atypical endometrial hyperplasia (AEH) coexisting with early-stage endometrial cancer (EC). We aimed to assess the staining patterns of selected CKs (CK7, CK19, CK20, CK AE1/AE3) in 74 patients with coexisting AEH and EC by independently analyzing both morphological variables. Specimens were collected from women with AEH and EC who underwent surgical interventions between 2012 and 2019 at the Department of Obstetrics and Gynecology of Vilnius University Hospital "Santaros Klinikos" in Vilnius, Lithuania. Immunostaining was also qualitatively classified as being heterogeneous or intense. The results revealed heterogeneous CK7 expression in all AEH cases and intense staining in 95.95% cases of AEH. The heterogeneous expression of CK7 was detected in all EC specimens. Intense CK7 expression was observed in 95.09% cases of EC G1 and in all G2 ECs. Heterogenous CK19 expression was present in all AEH specimens with intense staining in 92.42% of cases. Heterogeneous CK19 expression was observed in all EC samples with intense expression in 86.27% cases of EC G1 and 100% cases of EC G2. Interestingly, a significant relationship was found when comparing the heterogeneous expression of CK19 between AEH and well-differentiated EC. A significant difference was reported in the intense expression of CK AE1/AE3 (<i>p</i> = 0.031; <i>p</i> = 0.029) between AEH and G2 ECs and in the intense expression of CK AE1/AE3 between G1 and G2 ECs. CK20 staining was not a characteristic feature for AEH and early-stage EC. CK staining is present either in AEH or in early-stage endometrioid-subtype EC in different manners. Heterogeneous CK19 expression was significantly more common in AEH than in EC. CK20 expression was not associated with either AEH nor early-stage EC. An intense expression of CK AE1/AE3 was mainly present in moderately differentiated ECs, whereas the intense reactivity of AE1/AE3 showed a significant difference in well to moderately differentiated uterine tumors. The clinical implication of CK staining may aid in the more accurate diagnosis of AEH and early-stage EC as well as detect micrometastases leading to better oncological outcomes.