Masoud Moslehi, Majid Assadi Figure 1. (Left upper) Anterior and (left lower) poste- rior projections of the 131I whole body scan show mild bilateral 131I uptake in the lower chest region compared with the mediastinum. (Right lower) Right and (right upper) left lateral projections of the chest confirm that the 131I activity is in the bilateral breast regions have a history of previous lactation [5], or hyper- prolactinaemia [3], or other pathological causes such as benign breast diseases [1, 6, 7], is well docu- mented; however, bilateral 131I uptake by the non- lactating breasts of single women with negative examination for galactorrhoea has rarely been re- ported [5]. Radioiodine uptake within the mammary gland has been reported in both lactating and non-lacta- ting women [4, 5]. There are four different patterns of breast uptake, full, focal, crescentic, and irreg- ular, and uptake may be unilateral or bilateral [9]. Additional lateral imaging with the breast suspen- ded was helpful for diagnosis. In addition, a discre- pancy between 131I and 201Tl uptake in the chest region may help to diagnose non-malignant breast uptake of 131I [3]. The mechanism of breast 131I accumulation re- mains uncertain. In most studies, the prolactin level is considered a major factor which may be induced by various drugs [10] or by prolactinoma [3]. In addi- tion, hypothyroidism, developed in preparation for 131I scanning and treatment, can induce mild hyper- prolactinaemia, with or without galactorrhoea [5]. Others have evaluated 23 non-pregnant women with breast uptake of 131I, including 4 single nulli- parous patients, 3 postmenopausal patients, and 16 other cases [5]. The mean time from discontin- uation of breastfeeding was 11.4 months. They found no remarkable differences in pattern of breast uptake in patients with normal and elevated prolactin levels, suggesting that prolactin may not play a principal role in breast 131I uptake [5]. In addi- tion, they showed that sensitization of breast tissue to prolactin due to previous prolonged periods of lactation was an unlikely explanation, because there were no consistent changes in the pattern or the relative intensity of breast uptake after a mean follow-up period of 11.4 months [5]. Furthermore, breast uptake was seen in four single nulliparous women who had never breastfed and one of these had a normal prolactin level and no galactorrhoea upon clinical examination, as in our case. In addi- tion, neither the dose or kind of radioiodine isotope nor the scanning time appeared to be an important factor for radioiodine breast uptake [5]. Therefore, the breast activity in our case might be idiopathic in origin. Bilateral breast uptake of 99mTc-MIBI during the menstrual cycle and in the postmenopausal course has been reported, with 58% and 72% of the cases in the first and fourth weeks of the menstrual cycle, respectively, and with 5% of postmenopausal women studied [11]. Our patient was in the fourth week of her menstrual cycle. Nevertheless, whether changes in hormonal levels during the menstrual cycle have any effect on 131I breast uptake requires further studies. In conclusion, this case showed bilateral uptake of 131I in a single nulliparous woman who had never breastfed; that could be misinterpreted as metas- tases. So, physicians should be aware of this pos- sible source of confusion even in this subgroup. A high degree of suspicion, accompanied by careful atten- tion, is needed for proper interpretation of positive radioiodine scans. R e f e r e n c e s 1. Allen T, Wiest P, Vela S, Hartshorne M, Crooks LA. I-131 uptake in the breast for thyroid cancer surveillance with biopsy- proven benign tissue. Clin Nucl Med 1998; 23: 585-7. 2. Oszukowska L, Knapska-Kucharska M, Lewiński A. Effects of drugs on the efficacy of radioiodine (|) therapy in hyper- thyroid patients. Arch Med Sci 2010; 6: 4-10. 3. Kao PF, Chang HY, Tsai MF, Lin KJ, Tzen KY, Chang CN. Breast uptake of iodine-131 mimicking lung metastases in a thyroid cancer patient with a pituitary tumour. Br J Radiol 2001; 74: 378-81. 4. Brzozowska M, Roach PJ. Timing and potential role of diag- nostic I-123 scintigraphy in assessing radioiodine breast uptake before ablation in postpartum women with thyroid cancer: a case series. Clin Nucl Med 2006; 31: 683-7. 5. Hammami MM, Bakheet S. Radioiodine breast uptake in nonbreastfeeding women: clinical and scintigraphic cha- racteristics. J Nucl Med 1996; 37: 26-31. 6. Serafini A, Sfakianakis G, Georgiou M, Morris J. Breast cyst simulating metastases on iodine-131 imaging in thyroid carcinoma. J Nucl Med 1998; 39: 1910-2. 7. Bakheet SM, Powe J, Hammami MM. Radioiodine uptake in the chest. J Nucl Med 1997; 38: 984-6. 8. Hosseini M, Houshmand M, Ebrahimi A. Breast cancer risk not only was not associated with CYP17/A2 allele but also was related to A1 allele. Arch Med Sci 2009; 5: 103-6. 576 Arch Med Sci 3, June / 2012