Objective. This study aimed at evaluating the expression of tyrosine kinase receptors c-kit, (platelet-derived growth factor receptor-α (PDGFR-α), and PDGFR-β in ovarian granulosa cell tumors (GCTs). Study design. Primary ovarian GCT specimens were obtained for immunohistochemical staining.The expressions of c-kit, PDGFR-α, and PDGFR-β were analyzed and scored by a semiquantitative (SQ) method. Normal ovarian tissue from the same patients' specimens served as internal controls. Results. A total of 21 specimens were available for evaluation. C-kit was expressed in only 2 samples, whereas both PDGFR-α and PDGFR-β stained positive in 100% of tumors. PDGFR targets demonstrated strong positive expression in intensity and amount of tissue stained. Normal ovarian tissue demonstrated complete absence of staining for all 3 antibodies evaluated. Conclusions. The data demonstrated significant expression of PDGFR targets of imatinib mesylate in GCTs, whereas normal ovarian tissues had a complete absence of staining.This expression profile provides the rationale to investigate the role of imatinib mesylate in PDGFR-positive GCTs. © 2008 by the Society for Gynecologic Investigation.