Pitfall of I-131 whole body scan: a mucinous adenocarcinoma of the ovary

Pitfall of I-131 whole body scan: a mucinous adenocarcinoma of the ovary

Ali Sellem^1,&, Issam Msakni², Wassim Elajmi¹, Hatem Hammami¹

¹Nuclear Medicine Department, Military Hospital of Tunis, Tunis, Tunisia, ²Pathology Department, Military Hospital of Tunis, Tunis, Tunisia

^&Corresponding author
Ali Sellem, Nuclear Medicine Department, Military Hospital of Tunis, Tunis, Tunisia

Introduction    

Radioiodine is used for treating differentiated thyroid carcinoma [1]. The presence of uptake sites on the whole body scanning (WBS) following iodine 131 (I-131) may be caused by physiological radioiodine uptake, thyroid remnants or metastasis. However, the presence of unusual lesions may cause a false-positive results on radioiodine WBS; therefore, it is imperative to carefully evaluate abnormal scans in order to appropriately manage patients with differentiated thyroid cancer (DTC) [1]. We herein report an interesting case of false positive radioiodine uptake on an ovarian mucinous adenocarcinoma.

Patient and observation     

A 57-year-old female patient underwent total thyroidectomy. Histopathology revealed a follicular thyroid carcinoma (pT1bNxMx). Four weeks later she received, with thyroid hormone withdrawal, 3.7 GBq of 131I as a treatment. At this time, the serum thyroglobulin level was 2.7 ng/mL, TSH was 73 µIU/ml and antithyroglobulin antibody level was less than 20 IU/mL. Five days after the treatment, WBS (Figure 1) showed mild uptake in the neck, representing thyroid remnants, and a large and a high heterogeneous radioiodine accumulation in the median lower abdomen and pelvis confirmed by Single Photon Emission Computed Tomography (SPECT) (Figure 2). An ultrasound showed a right adnexal mass measuring 126 mm with a double tissue and cystic components with heterogeneous vascularization on color Doppler (Figure 3). The patient underwent a hysterectomy with bilateral oophorectomy. Pathological examination found a mucinous adenocarcinoma of the right ovary (Figure 4).

Discussion     

Ovarian radioiodine uptake at post-therapy WBS may occur in benign or malignant conditions [2-4]. Pathology examination is the only way to differentiate between the two conditions. The benign pathological diagnosis can be a benign thyroid tissue (struma ovarii) [2], a benign mucinous ovarian cystadenoma [5, 6] and an ovarian endometriosis cyst [2]. The malignant conditions were metastasis of thyroid cancer cells to ovary and thyroid cancer originating from embryonic thyroid tissue in the ovary, which may also result in focal ovarian uptake [2]. To our knowledge, this is the first case of false-positive radioiodine uptake in an ovarian mucinous adenocarcinoma. The suggested mechanisms of radioiodine uptake in the ovarian cystadenoma include increased vascularity and capillary permeability [7].

Conclusion     

It is important to recognize the physiological and pathological aetiologies (unrelated to thyroid) that demonstrate 131 I uptake and may lead to false positif 131 I scan in patients of DTC.

Competing interests     

The authors declare no competing interests.

Authors' contributions     

Dr SELLEM, Dr HAMMAMI and Dr ELAJMI discussed the case and further explored this uptake. Dr MSAKNI allowed to make the diagnosis. Dr SELLEM wrote this clinical case. All authors have read and agreed to the final version of this manuscript.

Figures     

Figure 1: post-therapeutic whole body scanning showing a mild uptake in the neck (thyroid remnants), and a large radioiodine accumulation in the median lower abdomen and pelvis

Figure 2: SPECT of the pelvis showing a large and heterogeneous radioiodine accumulation

Figure 3: ultrasonography showing a right adnexal mass measuring 126 mm with a double tissue and cystic components

Figure 4: HEx250: mucinous adenocarcinoma of the ovary, mucinous glands in a fibrous stroma

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