An unusual case of a false-positive iodine-131 whole body scan in a patient with papillary thyroid cancer

A false-positive I-131 whole body scan (WBS) for lung uptake in a patient with papillary thyroid cancer, with replacement of his infiltrated esophagus with a left colon graft, is presented. The I-131 image, seen in the upper right lung field, was due to the contaminated colon graft lacking normal peristaltic movements, which was located in the right paramediastinal region. This finding was demonstrated by imaging the upper digestive tract with orally administered Tc-99m DTPA and by a barium x-ray.     

甲状腺癌^131I治疗后全身扫描盆腔浓聚^131I的临床分析

目的了解分化型甲状腺癌患者对治疗后全身显像（Rx—WBS）盆腔^131I明显浓聚情况及可能机制。方法①回顾性收集168例分化型甲状腺癌女性患者的资料（均有Rx．WBS图像）。②分析Rx-WBS图像特点,根据一定的纳入标准,最终纳入分析46例患者,并进行随访。结果盆腔^131I明显浓聚的46例（46处浓聚）患者中,6例同时存在2个可能的浓聚原因,2例目前浓聚原因不明。在50个导致盆腔^131I浓聚的原因中,与子宫相关41个,与子宫外相关9个,分别为直肠3个、膀胱5个、卵巢巧克力囊肿1个。在41个与子宫相关的浓聚因素中,结合SPECT／CT定位、B超、CT及随访结果发现,子宫肌瘤18个、节育器9个、子宫内膜增厚2个、官腔积液3个、月经期7个、子宫内膜腺肌症1个、孕囊1个。结论①当女性甲状腺癌患者的Rx．WBS图像在盆腔子宫水平出现^131I明显浓聚时,多与子宫相关,膀胱因素相对少见;当浓聚定位到子宫时,排除生理性摄取,多提示相关的妇科疾病,以子宫肌瘤多见。②膀胱、直肠所致的盆腔子宫水平^131I明显浓聚有其自身特点,相对易区分。（3）SPECT／CT对定位子宫浓聚^131I具有重要意义。     

False positive 131I whole body scans in thyroid cancer

Well differentiated thyroid cancer is a rare disease in the UK. It is the only cancer which, having metastasized, remains curable by radioisotope therapy with 131I. The main indication for administering repeat doses of 131I is the appearance of abnormal uptake in a whole body scan following diagnostic or therapeutic 131I administration. False positive scans, showing the presence of 131I uptake in the absence of residual thyroid tissue or metastases can occur, although they are uncommon. Unless recognized as a false positive, 131I uptake may result in diagnostic error and lead to administration of an unnecessary therapy dose. We describe a series of nine patients in whom the scans showed false positive uptake of 131I, including cases where the cause of the uptake is still uncertain. We demonstrate the common sites of false positive uptake, discuss the underlying mechanisms and suggest a systematic approach to the interpretation of whole body scans in order to prevent unnecessary treatment with 131I.     

131I whole body scintigraphy in thyroid cancer patients.

Iodine-131 is the most specific radionuclide to follow up patients with differentiated thyroid cancer (DTC). However there are some aspects that should be considered if 131I whole body scintigraphy (131I WBS) is performed. 1) Several prior conditions, including a bTSH above 30 mU/l and an urinary iodine excretion below 100-150 micrograms/g Crea, should be fulfilled. 2) Only about two thirds of metastases from DTC accumulate iodine. Therefore, in addition to 131I WBS, there is a need for other nonspecific tracers such as 99mTc Tetrofosmin WBS, 99mTc Sestamibi WBS or F-18 FDG PET to detect also iodine negative recurrences or metastases. There new tracers, especially F-18 FDG PET have demonstrated a very high detection rate of iodine negative metastases with mostly low differentiation. 3) The sensitivity of 131I WBS depends on the administered dose. Whereas the sensitivity of a diagnostic 131I WBS (up to 185 MBq) is below 60%, the value for a post-therapeutic 131I WBS (after 3700-7400 MBq) increases up to 75%. This means that in case of elevated serum thyroglobulin, iodine positive metastases cannot be excluded until WBS after 131I therapy is performed. 4) In patients with elevated serum thyroglobulin and/or known metastases, who are scheduled for 131I treatment, the question arises whether a diagnostic 131I WBS should be performed and if so, which dose should be administered to avoid thyroid stunning. There is evidence in the literature that the dose for a pre-therapeutic diagnostic 131I WBS should not exceed 74 MBq. 5) Despite the high specificity of 131I WBS, several pitfalls of iodine accumulation in non-malignant diseases and malignancies of other origin than thyroid cancer should be taken into account.     

131I全身显像及血清甲状腺球蛋白测定在分化型甲状腺癌治疗随访中的作用

目的 评价131I全身显像联合血清甲状腺球蛋白(Tg)测定在分化型甲状腺癌(DTC)131I治疗随访中的临床应用价值。 方法 153例经手术病理确诊为DTC的患者,均在术后接受了1次以上的131I治疗,每次剂量为1.85~9.25 GBq,131I治疗前测定血清Tg,治疗5 d后进行131I全身显像。 结果 153例行131I治疗的DTC患者共行血清Tg和131I全身显像检查各为262次,其中55.6%(85/153)的患者的血清Tg水平与131I全身显像均异常,13.7%(21/153)的患者两者均为正常,30.7%(47/153)的患者两者结果不一致,不一致的47例患者经其他影像学检查证实19例131I全身显像异常的患者中有13例异常,28例血清Tg异常的患者中有25例异常。血清Tg诊断DTC转移的灵敏度和特异度分别为89%(110/123)和90%(27/30),而131I全身显像的灵敏度和特异度分别为79.6%(98/123)和80%(24/30)。 结论 DTC手术及131I治疗后,常规进行血清Tg测定和131I全身显像检查,对术后判定复发转移灶及制定最佳131I诊疗计划、评价131I疗效具有重要的临床应用价值。     

Tg升高131I显像阴性的甲状腺癌患者131I疗效评价

目的　评价甲状腺球蛋白 (Tg)升高但1 31 I全身显像 (WBI)未见局部1 31 I浓聚的分化型甲状腺癌患者1 31 I治疗的疗效。方法　经甲状腺次全切除术后常规1 31 I去除残余甲状腺组织的分化型甲状腺癌患者 2 6例 ,血清Tg升高 ,WBI未见局部放射性浓聚。分为试验组 16例 ,行 3 .7～ 7.4GBq1 31 I治疗 ;对照组 10例 ,Tg升高但未行1 31 I治疗。分别随访监测Tg水平变化。结果　随访半年后试验组Tg由( 2 1.3± 13 .7) μg L明显降至 ( 10 .8± 4.7) μg L(t=2 .43 8,P <0 .0 5 ) ,对照组Tg则明显增高 (t=2 .672 ,P <0 .0 5 ) ,由 ( 18.9± 11.6) μg L增至 ( 2 9.8± 15 .3 ) μg L。 结论　Tg升高而WBI未见局部放射性浓聚的分化型甲状腺癌患者应密切随访 ,当Tg大于 10 μg L时应常规行1 31 I治疗     

Substernal thyroid carcinoma detected by 67Ga scan in a patient with normal 131I scan

A patient with a superior mediastinal mass on an admission chest radiograph was initially evaluated by an 131I thyroid scan which failed to demonstrate a substernal thyroid. However, the tomographic 67Ga scan clearly showed an abnormal uptake in the area corresponding to the mass lesion on radiographic examination. Subsequent resection and biopsy of the substernal mass revealed a poorly differentiated follicular carcinoma with foci of anaplastic carcinoma. The differential diagnosis of the anterior mediastinal mass and the usefullness of the tomographic gallium scan are briefly discussed.     

Iodine 131 uptake in a pleuropericardial cyst: case report of a false-positive radioiodine total body scan result in a patient with a thyroid cancer

An uptake of iodine 131 was casually discovered in the precordial region of a patient with a thyroid cancer and corresponded to a pleuropericardial cyst. Offprint requests to: M. Schlumberger     

The early detection of metastatic differentiated thyroid cancer using 131I total body scan and treatment with 131I

With the purpose of achieving early detection and performing 131I therapy for metastatic lesions of differentiated thyroid cancer, we studied the clinical findings in 132 patients who underwent 131I total body scanning (131I TBS) between 1981 and 1990. Metastatic lesions were detected only by 131I TBS in 24 (18%) of the 132 patients. Of the 49 patients treated with 131I for metastases, 27 (55%) underwent total thyroidectomy and then had their metastatic lesions treated by 131I less than one year later. In the remaining 22 patients (45%), the metastatic lesions were treated with 131I from 1 to 31 years (mean: 8.4 years) after the initial thyroidectomy. We determined the optimal timing of 131I TBS following radical thyroidectomy to be 3-4 weeks by sequential measurement of the serum thyroid hormones, TSH, and Tg, and determination of the 123I uptake in residual or metastatic cancer of the neck after thyroidectomy. 131I TBS with simultaneous serum Tg determination were performed in 52 patients with metastases. Scans were positive in 43 of the 52 (83%) and the serum Tg level was greater than 10 ng/ml in 46 of the 52 (88%). Serum Tg was elevated in 9 patients with negative scans, while low Tg levels were found in 6 patients with positive scans. 131I therapy was effective in 49 of the 65 treated patients (75%), including 5 cures. Two patients worsened and 6 died. These 8 patients were all older than 56 years of age. Post-therapeutic 131I TBS demonstrated unsuspected metastatic lesions in 7 patients and had a higher detection rate for metastatic lesions than diagnostic 131I TBS. We conclude that 131I TBS with simultaneous Tg determination should be performed to detect metastatic lesions in all patients following positively total thyroidectomy for differentiated thyroid cancer, and that 131I treatment should be given when positive 131I uptake is detected in metastatic or residual cancer.     

Silent parathyroid adenoma mistakenly interpreted on FDG-PET as thyroid cancer metastasis in a patient with elevated thyroglobulin and negative I-131 whole body scan and removed by radioguided minimally invasive surgery

Detection of recurrent and metastatic thyroid cancer remains a considerable challenge in patients presenting with rising thyroglobulin levels but with negative I-131 whole body scintigraphy. Such is the case in this patient with follicular thyroid cancer in whom subsequent FDG PET scanning showed a solitary hypermetabolic cervical lesion. With definitive management and multidisciplinary approach in mind, radioguided surgical excision came into play through the use of Tc-99m sestamibi, leading to successful removal of the lesion. Histopathology, however, revealed a parathyroid adenoma. This highlights the importance of considering differential diagnoses in apparent cases of recurrence to avoid potential pitfalls.     

False-positive whole-body scan after I-131 therapy in a patient with intestinal scar

The I-131 whole-body scan is a useful test to investigate the presence of metastatic disease of thyroid cancer after thyroidectomy. A 53-year-old woman received I-131 4 months after total thyroidectomy for papillary thyroid carcinoma for postsurgical ablation of the residual tumor cells. Whole-body scan demonstrated focal uptake of I-131 in the right iliac fossa that persisted 2 days later even after administration of laxatives. Computed tomography of this area showed only focal bowel scar presumably resulting from a complicated appendectomy 31 years ago. Intestinal adhesions accumulate I-131 and give false-positive activity on whole-body I-131 scans.     

False-positive I-131 accumulation in a liver cyst in a patient with thyroid carcinoma

Iodine-131 uptake was seen in the right upper abdominal quadrant of a patient with postoperative differentiated thyroid cancer that corresponded with a large liver cyst.     

131I治疗分化型甲状腺癌转移灶中甲状腺球蛋白测定和131I-全身显像的意义

目的探讨分化型甲状腺癌转移灶治疗中131I-全身显像(131I-WBS)和甲状腺球蛋白(Tg)测定的意义。方法39例分化型甲状腺癌患者术后4～6周用131I行首次清除残余甲状腺治疗,3～6个月后重复治疗,治疗中131I-WBS和Tg测定同期完成。结果在首次清除残余甲状腺治疗时显像发现淋巴、肺及骨转移灶有11例,其余转移灶于重复治疗时发现。131I治疗分化型甲状腺癌转移灶,以淋巴转移效果最好,肺转移次之,骨转移最差。有8例患者(20.5%)Tg测定与131I-WBS不符。结论131I治疗分化型甲状腺癌转移灶效果好,患者存活率高;131I-WBS和Tg测定在分化型甲状腺癌随访中应联合应用,互相补充。     

Unusual extrathyroidal iodine accumulation in a post-ablative I-131 scan

A case of iodine-131 accumulation in the gall bladder following an ablative dose for thyroid carcinoma is presented.