Advanced-Stage Gonadal Dysgerminoma in a Patient With a Previous Diagnosis of Familial Swyer Syndrome: A Very Rare Genetic Entity.

Introduction: Swyer syndrome is a genetic abnormality characterized by a 46,XY karyotype in a phenotypically female individual. Affected individuals typically have average or tall stature, unambiguous genitalia at birth, the presence of Müllerian structures, and bilateral streak gonads. Familial Swyer syndrome is extremely rare, and we identified only two case reports describing families with two and three sisters affected by this syndrome. Individuals with Swyer syndrome have an increased risk of developing gonadal malignancies. Case: A 19-year-old patient with primary amenorrhea, who had been followed up with a diagnosis of Swyer syndrome, was referred to our hospital due to a complaint of progressive abdominal distension and a 5-month history of lower abdominal pain. Karyotype analysis had been performed at another hospital when her older sibling was diagnosed with Swyer syndrome. However, she did not undergo bilateral gonadectomy after the diagnosis was confirmed, as her family postponed the procedure due to the COVID-19 pandemic. Surgical debulking of ovarian cancer was performed, and histopathology revealed a dysgerminoma, FIGO Stage IIIC. Conclusion: Early diagnosis of Swyer syndrome is essential, considering the significant risk of malignant gonadal tumors that may arise at an early age. Prepubertal female siblings of patients diagnosed with Swyer syndrome should be screened. Early diagnosis and prompt prophylactic gonadectomy can allow for a conservative treatment plan that may preserve fertility and improve patient survival.