PMC7568143_01
Ultrasonographic suspicious features of the large solid hypoechoic and taller-than-wide shape thyroid nodule located in the mid-inferior part of the left lobe (a), which showed significant tracer uptake at 18F-FDG PET/CT (arrow, (b)).
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US revealed a multinodular goitre with a prevalent 4 cm hypoechoic nodule with taller-than-wide shape in the mid-lower part of left thyroid lobe which was deemed at high risk for malignancy (European Thyroid Imaging and Reporting Data System (EU-TIRADS) 5) (Figure 1(a)); no pathological lymph nodes were detected. Because of the suspicious features of the left thyroid nodule, 18F-FDG PET/CT was performed, which showed intense uptake (standardized uptake value (SUV) max: 14; SUV ratio: 7.3; this latter defined as the ratio between the SUV of the nodule and that of the contralateral normal thyroid parenchyma) (Figure 1(b)).
Histology after thyroidectomy showing a tall-cell variant of papillary thyroid carcinoma: papillary architecture neoplasm consisting of proliferation of elongated cells with a large eosinophilic cytoplasm, "ground glass" nuclei, and evident nuclear grooves and pseudoinclusions (haematoxylin-eosin stain, 40X, (a)). The tumour showed scattered thyroglobulin cytoplasmatic staining of different intensity (20X, (b)) and strong and diffuse CK19 cytoplasmatic staining (40X, (c)). Immunohistochemical staining was performed using specific antibodies by indirect biotin streptavidin 3, 3'-diaminobenzidine (DAB) system.
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On histology, the large left thyroid nodule proved to be a tall-cell variant of PTC (pT3 pNx) which infiltrated the capsule, reached the fatty tissue, and invaded the vessels (Figure 2(a)). Tg (Figure 2(b)) and diffuse strong cytoplasmatic and membrane positivity for cytokeratin 19 (Figure 2(c)), an integral protein of the cytoskeleton of the epithelial cells which is highly expressed in PTC. The thyroid tumour was classified as stage II, and the patient as being at intermediate risk of recurrence.
During the fourth year of follow-up after surgery and radioactive 131I therapy, ultrasonography showed small (maximum 1.5 cm) suspicious laterocervical lymph nodes with oval shape and no visible hilum (a, b, arrows).
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During the fourth year of follow-up, neck US revealed a few (diameter 1.0-1.5 cm) oval laterocervical lymph nodes, with no visible hilum and focal hyperechogenicity at levels III and IV (Figures 3(a) and 3(b)), which aroused the suspicion of recurrence; serum Tg levels on L-thyroxine therapy and anti-Tg antibodies remained undetectable.
Fine needle aspiration cytology of the left laterocervical lymph-node recurrence detected during the fourth year of follow-up after surgery and radioactive 131I therapy, which showed three-dimensional papillary flaps of medium size cells with pseudoinclusions and grooves which proved compatible with metastasis of papillary thyroid carcinoma (ThinPrep method, Papanicolaou stain, 40X).
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Washout Tg levels proved "negative" (0.24 ng/ml); by contrast, FNAC showed epithelial cells with irregular nuclei and nuclear pseudoinclusions suggestive of PTC metastasis (Figure 4).
Histology of lymph node metastasis (first recurrence detected during the fourth year of follow-up after surgery and radioactive 131I therapy) of tall-cell variant of papillary thyroid carcinoma: proliferation of cells with a large eosinophilic cytoplasm, "ground glass" nuclei, and evident nuclear grooves and pseudoinclusions (left side) and residual patrimonial lymphoid tissue (right side) (haematoxylin-eosin stain, 40X, (a)). The neoplastic thyroid cells showed scattered thyroglobulin cytoplasmatic staining of different intensity (40X, (b)) and diffuse strong cytoplasmatic CK19 staining (40X, (c)). Immunohistochemical staining was performed using specific antibodies by indirect biotin streptavidin 3, 3'-diaminobenzidine (DAB) system.
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Tg (Figure 5(b)) and diffuse strong positivity for CK 19 (Figure 5(c)). The next year following lymphadenectomy, neck US was unremarkable, and serum Tg levels remained undetectable.
Ultrasonographic features of second nodal recurrences (6 years after surgery and radioactive iodine 131I therapy) of papillary thyroid carcinoma (two laterocervical metastatic hypoechoic lymph nodes, 2.2 cm and 1 cm, respectively) with irregular shape, no visible hilum and focal hyperechogenicity ((a), arrows). At 18F-FDG PET/CT, both lymph nodes showed significant tracer uptake (arrows) (the larger one: SUV max: 20.7; the smaller one: SUV max: 11) (b).
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US confirmed a 20 mm pathological (hypoechoic, with irregular shape, no visible hilum, and focal hyperechogenicity) lymph node in the left supraclavicular region (level IV) (Figure 6(a)) and a smaller one (10 mm) with the same features in the paratracheal region (level VI). 18F-FDG PET/CT showed significant tracer uptake (SUV max: 20.7) by left supraclavicular lymph node and, to a lesser extent (SUV max: 11), by left paratracheal lymph node (Figure 6(b)).