PMC4746842_01
(a) Gross specimen showing nodular enlargement of thyroid with blackish discoloration of the right lobe. (b) Microscopic features showing polygonal to spindle cells, in an organoid pattern with clumped chromatin, abundant cytoplasm, and areas of necrosis, focal hemorrhage, copious extracellular brownish black melanin pigment (arrow). (c) Immunohistochemistry right lobe shows tumor cells with brownish-black pigment showing strong cytoplasmic positivity with HMB45. (d) Immunohistochemistry left lobe shows tumor cells with brownish-black pigment showing strong cytoplasmic positivity with calcitonin
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F1
Gross findings showed enlargement of both lobes of thyroid with blackish discoloration of right lobe [Figure 1a]. The majority of tumor cells showed intracellular melanin deposition [Figure 1b]. Immunohistochemistry showed positivity with HMB45 in right lobe [Figure 1c] calcitonin in left lobe [Figure 1d].
Coronal and axial section of fluorine-18 fluorodeoxyglucose positron emission tomography/computed tomography showing intensely hypermetabolic hypo dense intraluminal filling defect right internal jugular vein, external jugular vein, subclavian vein confluencing at the right innominate vein with inferior extension into superior vena cava (arrow) and a small metabolically active pretracheal lymph node (dotted arrow)
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F2
There was no residual thyroid in the thyroid bed, however, a small metabolically active pretracheal lymph node was noted [Figure 2].
Coronal fluorine-18 fluorodeoxyglucose positron emission tomography/computed tomography postradiotherapy showing complete metabolic regression in the intravascular tumor (arrow) with significant reduction in the tumor thrombus load and better contrast passage through the superior vena cava (dotted arrow)
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F3
F18 FDG PET//CT done subsequently revealed complete metabolic regression in the intravascular tumor with significant reduction in the tumor thrombus and better contrast passage through the SVC [Figure 3]. Follow-up at 3 months patient continued to be symptom-free with complete disappearance of the boggy neck swelling.
Color Doppler of the neck showing grossly shrunken thrombus in the right internal jugular vein with absent flow (arrow) and normal flow through the left innominate vein (dotted arrow)
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F4
Color Doppler of the neck revealed significantly shrunken thrombus in the right IJV with flow void and normal flow through the left innominate vein [Figure 4].
Coronal and sagittal contrast computed tomography chest showing hypodense filling defect in the right internal jugular vein reduced in extent with tiny calcifications, suggesting chronic thrombus (arrows), and patent left innominate vein filled with contrast streaking past the thrombus into superior vena cava (dotted arrows)
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F5
A contrast CT chest showed non-enhancing hypodense filling defect reduced in extent with tiny calcifications in the right IJV, EJV, subclavian veins suggesting chronic bland venous thrombus [Figure 5].