The fifth leading cause of cancer-related deaths among women in the United States is ovarian cancer. An estimated 21,980 new cases and 14,270 estimated deaths occurred nationwide in 2014. More than two-thirds of cases of ovarian cancer are diagnosed at stage III or IV when the peritoneal cavity or other organs are affected. Primary appendiceal malignant neoplasms may mimic advanced-stage ovarian cancer and can be misdiagnosed because of its presentation as a palpable adnexal mass. The authors describe a 42-year-old woman who was admitted to the department of obstetrics and gynecology to receive treatment for presumed advanced-stage ovarian cancer. She subsequently received a diagnosis of primary pseudomyxoma peritonei metastatic to the ovaries, mimicking a primary ovarian cancer by osteopathic structural examination findings, serum tumor markers, surgical exploration, and histopathologic confirmation.