Background: Ovarian cancer is one of the most common cancers among females worldwide. Its 
pathogenesis is not well understood till now. FLOT-1 is expressed in a wide range of normal and 
neoplastic tissues and has emerged as an important regulator cellular adhesion, proliferation, and 
metastasis. Its role in ovarian serous carcinogenesis is not clear and needs further studies. Methods:
The present study comprised 72 cases of serous ovarian tumors including; 50 (69.44%) cases of serous 
ovarian carcinoma, 12 (16.67%) cases of borderline serous ovarian tumors and 10 (13.89%) cases of 
serous ovarian cyst-adenoma. Immunohistochemistry for FLOT-1 antibody was performed using the 
avidin biotin-peroxidase complex method. Results: FLOT-1 was positive in 54% of serous ovarian 
carcinoma cases, 50% of borderline cases were positive and all serous cystadenoma cases were 
negative. Statistically significant association was detected between FLOT-1 expression and grade of 
differentiation of serous ovarian carcinoma cases (p=0.000). Meanwhile, no statistically significant 
association was found between FLOT-1 expression and age, tumor size, tumor bi-laterality and tumor 
stage (p=0.179, 0.643, 0.093, 0.187 respectively). In serous borderline cases, there were no statistically 
significant association between FLOT-1 expression and age, tumor size and tumor bi-laterality (p=
0.558, 0.558, 0.121 respectively). Conclusions: FLOT-1 expression is significantly associated with 
poor prognostic factors and thus can be used as a prognostic indicator for serous ovarian carcinoma 
patients.