## 4 Discussion
### Diagnosis Approach  
Location in the right ovary of struma ovarii is infrequent. In the literature, the tumor was described more often on the left side, which was true in our patients. Regarding the dimension of the tumor, [PERSON] et al. reported in their study that the tumor sizes ranged from 2.5 to 25.0 cm, which is consistent with our findings [12]. Clinical symptoms that may manifest due to the presence of a struma ovarii are lower abdominal pain (50% of cases), palpable lower abdominal mass, abnormal vaginal bleeding, ascites (one-third of cases), hydrothorax, elevated thyroid function (5-8%), and, rarely, thyroid tumors [13; 14]. Except for hydrothorax, all symptoms were present in the participants in our study.  
The occurrence of ascites in patients with struma ovarii has been observed to vary, ranging between 17 and 33%, according to several authors [15; 16]. The precise mechanisms of ascites formation in patients with struma ovarii is currently unclear, but it has been indicated that if ascites is present, it usually resolves spontaneously after tumor excision. In our study, we had only a single case with ascites.  
Struma ovarii is usually non-functional, but 8% can present with thyrotoxicosis, which is likely to be mediated by a mechanism different from classic thyroid hyperthyroidism [5]. It is postulated that struma ovarii is an autonomous hormone-secreting tumor, or thyrotoxicosis, which may be due to autoimmune stimulation of the normal thyroid gland [17].  
Our data agree with the study of [PERSON], showing the same percentage of cases with hyperthyroidism (8%). In our cases, the hyperthyroidism symptoms went away five weeks after surgery.  
Figure 11: Thyroid papillary carcinoma. HE, 10\(\times\).  
Even though CA-125 is a non-specific marker for struma ovarii diagnosis, it is required as a laboratory test for every ovarian tumor. However, there are data in the literature proving an increase in CA-125 in the setting of struma ovarii. For instance, in their study in 2009, [PERSON] and [PERSON] described an increased level of CA-125 in only 8 cases of struma ovarii [18]. In our study, we identified two cases of struma ovarii with a CA-125 slight increase of 38 and 45 Ui/ml, respectively; however, these values are lower than those reported in other studies varying between 224-5218 Ui/ml [19]. For this reason, in the differential diagnosis of ovarian formations with high levels of CA-125, struma ovarii should also be considered.  
Pre-operative diagnosis is very difficult because US computer tomography (CT) and magnetic resonance imaging (MRI) are not specific enough. With these techniques, we can only see adnexal masses consisting of solid and cystic parts. This is supported by our research, as none of our patients had been diagnosed with struma ovarii prior to surgery. Struma ovarii can be diagnosed using Doppler flow. Blood flow signals detected from the core of the echoic lesion, as well as low resistance to flow, are more common in struma ovarii, but they can also be found in ovarian cancer [20; 21]. This US aspect was displayed in two women in our study. It is clear that if we suspect ovarian teratoma and the Doppler exam shows central vascularization, it is almost certainly struma ovarii. In general, struma ovarii appeared as a smooth marginated multicystic mass with high attenuation lesions on precontrast scans on CT [22]. On T1- and T2- weighted images, the cystic spaces demonstrate both high and low signal intensities [23]. [PERSON] et al. revealed that struma ovarii contains a multilobulated complex mass with thickened septa, multiple cysts with varying signal intensities depending on the viscosity of the fluid, and enhanced solid components on MRI [24; 25]. Only pre-operative scintigraphy with iodine (\({}^{131}\)I) could show active thyroid tissue in the small pelvis. CT, MRI, and scintigraphy were not performed on any of our patients. Because of its rarity, modest traits, and lack of clinical suspicion, struma ovarii frequently goes undetected during intraoperative consultation [26].