ABSTRAK Latar belakang: Frekuensi tumor ovarium serosum ganas menempati urutan tertinggi dari seluruh keganasan ovarium di dunia barat 80-85 , sesuai dengan arsip Departemen Patologi Anatomik Fakultas Kedokteran Universitas Indonesia FKUI /Rumah Sakit Cipto Mangunkusumo RSCM selama 10 tahun 2004-2013 , sebanyak 200 kasus 21,4 dari seluruh keganasan ovarium. GLUT-1 dapat digunakan sebagai penanda perangai biologik tumor ovarium serosum. Tujuan penelitian ini membandingkan ekspresi GLUT-1 pada tumor ovarium serosum borderline dan ganas serta faktor risiko.Metode: Penelitian ini menggunakan metode potong lintang. Sampel terdiri atas 17 kasus untuk masing masing kelompok tumor ovarium serosum borderline dan ganas. Dilakukan pulasan GLUT-1 dengan penilaian berdasarkan intensitas dan jumlah sitoplasma dan/atau membran sel yang terpulas. Dilakukan penghitungan histoscore dan persentase setiap kasus dan dinilai ekspresi GLUT-1 berdasarkan titik potong kemudian dikelompokkan menjadi ekspresi rendah dan tinggi.Hasil: Pulasan GLUT-1 ekspresi rendah sama banyak dengan ekspresi tinggi. Sebagian besar kelompok tumor ovarium serosum borderline menunjukkan ekspresi rendah. Kelompok tumor ovarium serosum ganas sebagian besar menunjukkan ekspresi tinggi. Perbedaan ekspresi GLUT-1 antara tumor ovarium serosum borderline dan ganas, secara statistik bermakna p ABSTRACT Background : The frequency of serous malignant tumors of ovary occupies the highest order of all ovarian malignancies in the western world 80-85 , in accordance with Department of Anatomical Pathology, Faculty of Medicine University of Indonesia / Cipto Mangunkusumo hospital datas, for 10 years 2004-2013 , as many as 200 cases 21.4 of all ovarian malignancies. GLUT-1 can be used as a marker in differentiating biological behaviour of serous ovarian tumor. The aim of the study was to compare expression of GLUT-1 in serous borderline and malignant tumours of the ovary. Methods : This was cross-sectional study. Sample consists of 17 cases for each group, serous borderline and malignant tumor of ovary, stained with GLUT-1 antibody. Quantification was based on the intensity and distribution of cytoplasm and/or cell membrane. The appraisal was done with estimating histoscore and percentage of each case. Calculation result was assessed by GLUT-1 expression, based on the point of intersection and then grouped into low and high expression.Result : The GLUT-1 low expression results are equal with high expression. Low grade expression found in majority cases of serous borderline ovarian tumors group. Groups of serous malignant ovarian tumors largely exhibit high expression. These differences in Glut-1 expression among the borderline and malignant cases, are statistically significant p