Struma ovarii is a rare monodermal ovarian teratoma predominantly composed of mature thyroid tissue. While thyroid tissue may be present in 5–15% of dermoid cysts, the diagnosis of struma ovarii is reserved for tumors in which thyroid tissue comprises more than 50% of the lesion. It most commonly presents in women in the fourth to sixth decades of life. We present the case of a 24-year-old nulligravid woman who presented with progressive abdominal enlargement. Initial transrectal ultrasonography demonstrated an abdominopelvic mass suggestive of an ovarian neoplasm, while subsequent abdominal ultrasonography revealed a huge pelvo-abdominal cystic mass consistent with an ovarian new growth. The patient underwent exploratory laparotomy with right salpingo-oophorectomy for diagnostic and therapeutic management. Considering the patient’s young age and desire for fertility preservation, unilateral salpingo-oophorectomy was selected as the most appropriate surgical approach in the absence of capsular invasion or distant metastasis. Histopathologic examination confirmed struma ovarii of the right ovary with an associated right paratubal cyst, while the right fallopian tube showed no significant diagnostic abnormality. Postoperative recovery was uneventful, and the patient was discharged in stable condition. At one-month follow-up, she remained asymptomatic, with no evidence of ascites. Thyroid function tests, including serum thyroid hormone and thyroid-stimulating hormone levels, were within normal limits, and no thyroid suppression therapy was indicated. This case underscores the diagnostic difficulty of struma ovarii due to its nonspecific clinical and imaging findings, as well as its uncommon presentation in a young reproductive-age patient. Definitive diagnosis relies on histopathologic evaluation, and timely surgical management remains crucial in achieving favorable clinical outcomes.

Dr. Uzzhiel J. Flores is a physician from the Philippines currently practicing at Corazon Locsin Montelibano Memorial Regional Hospital. She earned a medical degree from Matias H. Aznar Memorial College of Medicine, Inc. and has developed strong interests in obstetrics and gynecology and complex clinical case management. Dr. Flores has been actively involved in patient care and academic discussions on her current 1st year of residency training. Dedicated to continuous professional growth, she aims to contribute to medical education and research through clinical case presentations and collaborative learning opportunities.