Palaniswamy Shanmuga S, Subramanyam Padma
Department of Nuclear Medicine and Molecular Imaging, Amrita Institute of Medical Sciences, Amrita Vishwavidyapeetham, Cochin, Kerala, India.
Indian J Endocrinol Metab. 2018 Nov-Dec;22(6):740-750. doi: 10.4103/ijem.IJEM_70_18.
Differentiated thyroid carcinoma (DTC) is the most common pathological type of thyroid carcinoma, which includes papillary and follicular subtypes. DTC is usually indolent, characterized by good prognosis, and long-term survival. Total thyroidectomy is the mainstay of treatment in DTC which is followed by diagnostic whole body 131I (WBI) scan. Like other primary malignancies of the head and neck, DTC follows a consistent pattern of spread in the cervical LNs. The central compartment, level VI and VII, is the first sentinel node followed by spread to the lateral compartments levels II-V, followed by the contralateral side. Inspite of nodal involvement, DTC usually have a favourable outcome. Presence of extrapulmonary distant metastases could predict a poor prognosis for high-dose I therapy. However, distant metastasis occurs often as a grave event and mortality rates vary depending on metastatic sites.
A range of rare I concentrating DTC deposits in sella, orbit, choroid, skeletal muscles, liver, skin, costochondral soft tissue, pancreas and kidney, and a few benign I concentrating sites are being depicted.
Metastatic sites from DTC can be easily identified by performing a whole body I (WBI) scan along with a stimulated thyroglobulin (Tg) estimation (TSH >30 uIU/ml). Apart from thyroid and thyroid-related diseases, certain benign non-thyroidal pathologies can concentrate radioiodine (I). From 13,000 of our patients who underwent radioiodine scan for thyroid cancer, we have selected a few cases of I concentrating benign and malignant lesions for illustration.
Out of 13000 DTC patients who underwent whole body I scintigraphy in our department from Jan 2007 till Mar 2018, 25 patients revealed benign sites of I uptake. 61 % patients had residual thyroid tissue with or without associated nodal involvement. Remaining patients had distant metastases. Rare sites of functioning thyroid metastases and benign sites of I 131 uptake have been selected for illustration.
Apart from the WBI (two-dimensional, planar) images, single-photon emission computed tomography-computed tomography (SPECT-CT) has been incremental in localizing benign lesions which greatly depends on their location. This pictorial review highlights the need to create an awareness to detect metastatic deposits of DTC at unexpected sites. Otherwise patients will need further investigation to rule out unsuspected sites of functioning distant metastases.
分化型甲状腺癌（DTC）是甲状腺癌最常见的病理类型，包括乳头状和滤泡状亚型。DTC通常生长缓慢，预后良好，生存期长。全甲状腺切除术是DTC的主要治疗方法，术后需进行诊断性全身131I（WBI）扫描。与其他头颈部原发性恶性肿瘤一样，DTC在颈部淋巴结的转移模式具有一致性。中央区，即Ⅵ和Ⅶ区，是首个前哨淋巴结，随后转移至Ⅱ-Ⅴ区的外侧区，然后是对侧。尽管有淋巴结受累，DTC通常预后良好。肺外远处转移的存在可能预示着高剂量I治疗预后不良。然而，远处转移通常是一个严重事件，死亡率因转移部位而异。
描述一系列罕见的I浓聚性DTC在蝶鞍、眼眶、脉络膜、骨骼肌、肝脏、皮肤、肋软骨软组织、胰腺和肾脏中的沉积情况，以及一些良性I浓聚部位。
通过进行全身I（WBI）扫描并测定刺激后的甲状腺球蛋白（Tg）（促甲状腺激素>30 μIU/ml），可以轻松识别DTC的转移部位。除甲状腺及甲状腺相关疾病外，某些良性非甲状腺疾病也可浓聚放射性碘（I）。从我们13000例接受甲状腺癌放射性碘扫描的患者中，我们挑选了一些I浓聚的良性和恶性病变病例进行说明。
在2007年1月至2018年3月期间在我们科室接受全身I闪烁扫描的13000例DTC患者中，25例显示有I摄取的良性部位。61%的患者有残余甲状腺组织，伴或不伴有相关淋巴结受累。其余患者有远处转移。已挑选出功能性甲状腺转移的罕见部位和I 131摄取的良性部位进行说明。
除了WBI（二维、平面）图像外，单光子发射计算机断层扫描-计算机断层扫描（SPECT-CT）在定位良性病变方面发挥了越来越大的作用，这在很大程度上取决于它们的位置。本图像综述强调有必要提高对在意外部位检测DTC转移灶的认识。否则，患者将需要进一步检查以排除未被怀疑的功能性远处转移部位。
