In gynecologic oncology, surgical and adjuvant therapy rely heavily on correct pathologic diagnosis. Thus, in-house review of outside pathologic slides and specimens has become routine within large tertiary referral centers. We sought to determine the impact of outside pathologic slide review on gynecologic oncology patient care and treatment. Gynecologic oncology cases between January 2007 and January 2012 were evaluated. Clinical information was gathered from comprehensive chart reviews and reports created after multidisciplinary treatment planning conferences. Discrepancies in diagnosis were identified as major if they resulted in a treatment alteration and minor if they did not impact care. Data were analyzed using descriptive statistics and the Fisher exact test. A total of 279 cases were identified and reviewed as part of the study--126 (45.2%) biopsy/cytology specimens and 153 (54.8%) surgical excision specimens. Minor discrepancies were noted in 25 reviewed cases (9%) and major discrepancies in 19 cases (6.8%). Among those patients in whom management was changed based on specialized pathologic review, 50% underwent additional surgery, 16% had their surgical plan modified, and 16% received adjuvant treatment or had their adjuvant treatment modified. In 235 cases (84.2%), institutional rereview of the outside slides/specimens did not result in a change in diagnosis. Diagnostic discrepancies were evenly distributed across all primary sites evaluated. The cost of outside pathologic review was estimated at $2,936 US dollars per change in diagnosis. Mandatory slide review in gynecologic oncology is important and results in diagnostic changes in approximately 16% of cases, with 43% of those changes impacting treatment.