Endometrial stromal sarcomas (ESS) are rare and understudied gynecologic mesenchymal neoplasms. These tumors can be confused with many other gynecologic and nongynecologic tumors due to their variegated morphologic appearance and nonspecific immunohistochemical profile. ESS can express cytokeratin (CK) and, therefore, may be misdiagnosed as carcinoma especially in extrauterine locations and when recurrence/metastasis is present. In this study, we investigated the expression of a wide spectrum of CKs consisting of AE1/3, CAM 5.2, HMCK, MNF116, CK5, CK6, CK7, CK8/18, CK14, CK17, CK19, and CK20 in 6 low-grade and 5 high-grade ESS. In addition, staining for estrogen receptor, progesterone receptor, CD10, and cyclin D1 was performed. Our results showed that CKs AE1/3, CAM 5.2, MNF116, and CK8/18 are more expressed in low-grade ESS, whereas high-grade ESS express more AE1/3 and CAM 5.2. In problematic cases, especially in recurrences or metastases, the immunohistochemical panel of antibodies AE1/3, MNF116, CAM 5.2, and CK8/18, together with other classic immunohistochemical markers CD10, cyclin D1, estrogen receptor, and progesterone receptor, may be helpful in the differential diagnosis between ESS and other gynecologic and nongynecologic malignancies.