Struma Ovarii is a rare variant of monodermal ovarian mature cystic teratoma consisting of thyroid tissue [1]. It comprises 1% of all ovarian tumours and 2.7% of all dermoid tumours [2]. It is usually a benign condition; however, malignant transformation occurs in less than 5% of them [3]. It is difficult to diagnose these cases preoperatively as there are no specific clinical, radiological or serum markers in the absence of thyroid abnormality. Most cases are diagnosed on histopathology [4,5]. A typical feature of struma ovarii on doppler is the presence of well-defined solid tissue with a smooth margin that is vascularised - “struma pearl’[6]. Subtle radiological signs and clinical suspicion can avoid extensive staging laparotomies in patients with struma ovarii. The purpose of reporting this case study is to describe a case of struma ovarii and go through a review of the literature to stress the importance of conservative management.

60-year-old patient with post-hysterectomy presented with dull aching lower abdominal pain for 3 months with no history of loss of appetite/weight or any symptoms of hyperthyroidism. General and systemic examinations were unremarkable. The thyroid was normal. Abdominal examination showed a transverse scar, no mass was palpable. On per speculum vault appeared normal. On bimanual examination a non-tender, cystic mass of 10x10cm arising from the pelvis was felt in the midline. Ultrasonography displayed a pelvic mass of 9.5x9.1cm with multiple septa and a solid nodule suggestive of ovarian neoplasm. CT pelvis revealed a large well defined thin-walled lobulated cystic mass measuring 11.8x10cm with calcific solid excrescence and few septations within arising from the right adnexa suggestive of ? ovarian neoplasm; no lymphadenopathy. On investigation, TSH 7.62 miu/L, Ca-125 4.8mIU/L, Ca19.9 <3mIU/L, C-Xray were normal. The patient underwent a Laparoscopic right salpingo-oophorectomy. Intraoperative findings included: no free fluid in the abdomen/pelvis, post hysterectomy status, left adnexa not visualised, right ovarian cyst measured 12x12cm with thick yellowish fluid, no normal ovarian tissue, POD and the rest of the viscera were normal.

Struma ovarii is defined as a mature teratoma comprising thyroid tissue exclusively or predominantly [7]. Most cases are diagnosed on histopathology [5]. It is difficult to diagnose struma ovarii preoperatively as there are no specific clinical, radiological or serum markers in the absence of thyroid abnormality. The incidence of thyroid hyperfunction is reported to be 5-8% in these patients [8]. Often they require extensive staging laparotomy for suspected ovarian malignancy.