PMC6684754_01
Skin metastasis. (A) Hematoxylin Eosin staining of histological slides, magnification 4 x 1. *indicates less differentiated areas. (B) Immunohistochemical staining of TTF-1, magnification 20 x 1.
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F1
The lesion was removed and the histological diagnosis suggested a thyroidal origin; the nodule was composed of epithelial cells arranged in follicular structures which contained amorphous material resembling thyroid colloid (Figure 1A). On immunohistochemical staining, neoplastic cells showed expression of TTF-1 (Figure 1B), Cytokeratin 7, and Thyroglobulin (Tg); thus, a diagnosis of probable metastasis from a follicular thyroid carcinoma (FTC) was made.
18FDG-PET scan showing lung uptake (A) and thyroid uptake (B). Computed Tomography Imaging of lung metastasis (C).
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F2
After collegial discussion with the surgeon, nuclear medicine specialist and pathologist, a total-body PET 18F-FDG scan (with a Siemens somatom sensation 16 biograph, Rome, Italy) was performed; this showed a lung metastasis with poor 18-FDG uptake (Figure 2A) and a left thyroid nodule with moderate 18-FDG uptake (Figure 2B). We then performed a total-body CT scan, which revealed a liver metastasis and confirmed the lung metastases (Figure 2C).
Thyroid tissue. Hematoxylin Eosin staining of histological slides, magnification 10 x 1.
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F3
100-200 ng of genomic DNA was extracted from FFPE thyroid tissues (A,B) and cutaneous metastasis (C,D) by using QIAamp DNA FFPE Tissue Kit (Qiagen, Hilden, Germany) and subjected to TERT promoter amplification (A,C) by PCR as described in Dono et al. and to NRAS exon 3 amplification (B,D) by PCR using 1.5 U Platinum Taq DNA polymerase (Thermo Fisher Scientific, Milan, Italy), 1x buffer, 2 mM MgCl2, 200 nM dNTPs, and 30 pmoles of Forward (5'gattcttacagaaaacaagtgg) and Reverse (5' taatgctcctagtacctagtgag) primers in a final volume of 50 mul. The amplified PCR products were then treated with ExoSap (GeHealthcare, Waukesha, USA) as recommended and both strands sequenced by dye terminator cycle sequencing (BigDye Terminator v3.1, Thermo Fisher). Nucleotide sequence detection was performed on an ABI Prism 3,500 Genetic Analyzer (Thermo Fisher) according to standard protocols. The sequence data were obtained by Mac Vector software analysis (MacVector Inc., North Carolina, USA).
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F4
While both tissues proved to be BRAF wild-type, the cutaneous metastasis was TERT promoter-mutated (g.1,295,228 C>T) (not shown and Figure 4C); in contrast, the primary thyroid lesion was negative for both molecular markers (not shown and Figure 4A). Interestingly, a NRAS Gln61Arg mutation co-occurring with the TERT mutation was found in the cutaneous metastasis (Figure 4D) but not in the primary carcinoma (Figure 4B).