Unusual case of hepatic metastasis in follicular thyroid carcinoma detected using I-131 whole body scintigraphy and single-photon emission computerized tomography/computerized tomography

A 55-year-old man underwent total thyroidectomy which revealed follicular thyroid carcinoma (FTC). After 1-month, his thyroid stimulating hormone (TSH) was >100 mIU/L and serum thyroglobulin was 26,500 ng/ml, he was referred for I-131 whole body scintigraphy (WBS) which showed uptake in neck, bilateral lungs and an intense uptake in the right side of abdomen [Figure 1]. Single-photon emission computerized tomography/computerized tomography (SPECT/CT) of abdomen localizes intense uptake in the upper abdomen to the lesion in the right lobe of liver [Figure 2]. He underwent high dose radioiodine therapy with the dose of 250 mCi (9.25 Gbq).

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Figure 1 Iodine-131 whole body scintigraphy shows uptake in neck, bilateral lung and in right upper abdomen

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Figure 2 Single-photon emission computerized tomography/computerized tomography of abdomen showing increased uptake in the lesion in right lobe of the liver

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Differentiated thyroid cancer (DTC) is the most common endocrine neoplasm. Distant metastases occur in up to 10% of patients with DTC. Larger primary tumor size, extracapsular extension, older age, certain histological variants, and distant metastases have all been identified as risk factors for poorer prognosis, often with a cumulative effect.[1] DTC metastases to the brain, eye, breast, liver, kidney, muscle, and skin are rare or relatively rare and often overlooked in clinical setting.[2] Metastasis to the liver from DTC is a rare event with a reported frequency of 0.5%. Metastatic liver involvement from DTC is nearly always multiple or diffuse and usually found along with other distant metastases (lung, bone and brain).[3] A review of the literature revealed that only 10 cases have been documented. Three were males and seven females with an average age of about 63 years (range from 32 to 85 years). Histologically, the primary tumor was identified as papillary in four patients,[45] follicular in five,[56789] and Hűrthle cell TC in one patients.[3] In two cases, the metastatic histological type was inconsistent with the primary tumor. The primary tumors were FTC and papillary thyroid carcinoma (PTC), while both their metastatic lesions were a follicular variant of PTC.[45] Transformation of histopathologic types may occur in liver metastases from DTC, therefore, a careful retrospective histological study is recommended.

Djenic et al. recently reported a solitary liver metastasis from follicular variant of PTC, which was surgically resected.[10] So our case will be the 12^thcase reported in literature. Most liver metastases from DTC were asymptomatic and were usually discovered incidentally as in our patient. The I-131 WBS combined with SPECT/CT scan plays an important role in increasing diagnostic accuracy, reducing pitfalls, and modifying therapeutic strategies.[11] Song et al. in their pictorial review highlights the diagnostic aspects of I 131-SPECT/CT for the localization and definition of rare metastases in DTC patient.[12] Our patient received I 131 treatment, because of multiple metastasis in lungs and bone. The survival rate after liver metastases is poor; however, it cannot be attributed to liver metastases alone, because it generally appeared after more metastases at other sites.