Abstract Background: Endometrial cancer (EC) is the most commonly diagnosed gynecologic malignancy globally; The etiology of EC is still unknown, but most of the risk factors are related to changes in hormonal patterns that occur in women. In the female reproductive tract, fibroblasts promote epithelial development and differentiation which responsible for extracellular matrix remodeling, survival and death. Fibroblast activation protein (FAP) is a cell surface antigen that expressed on reactive stromal fibroblasts of cancer epithelial cells and appears as an important factor in cancer-associated fibroblasts (CAF), which relevant in tumor development. FAP has effects on cell proliferation, migration, and invasion, which promote tumor growth. To date, only one study of FAP has been found on the endometrium. In addition, there have been no studies on the expression of FAP against endometrial carcinoma subtypes. Objective: This study was conducted to analyze the immunohistochemical expression of FAP in endometrial carcinoma sub subtypes. Methods: The study used 38 samples of paraffin blocks from endometrial carcinoma cases that had been diagnosed at the Laboratory of Anatomical Pathology, RSUP H. Adam Malik and the Department of Anatomical Pathology, Faculty of Medicine, Universitas Sumatera Utara. FAP expression was assessed using immunohistochemical staining of tumor cell cytoplasm and stroma. Expressions were assessed using the Quick Score method and were declared positive if the total score ? 3. Results: Immunohistochemical expression of FAP in endometrial carcinoma was the most positive in the endometrioid carcinoma subtype, namely 27 cases (77.14%). Keywords: endometrial carcinoma, cancer-associated fibroblasts, fibroblast activation protein

endometrial cancer

Fibroblast Activation Protein

cancer-associated fibroblast