PMC5122646_01
Neck lymph node (LN) shows metastatic extremely well differentiated papillary thyroid carcinoma (EWD-PTC) (A, H-E stain, x12.5 and inset x400) with focal positivity of CK19 (B, x400) in the first metastatic lesion. The left thyroid shows follicular variant papillary thyroid carcinoma (FVPTC) without capsular (arrow) invasion (C, H-E stain, x40 and inset x400) with focal positivity of CK19 (D, x40) and loss of CD56 (E, x40) in second episode. The LN also shows metastatic EWD-PTC (F, H-E stain, x12.5 and inset x400) with focal positivity of CK19 (G, x400) and CD56 (H, x400) in the second metastatic lesion. The skull lesion shows metastatic FVPTC (I, H-E stain, x100 and inset x400) with focal positivity of CK19 (J, x400) and CD56 (K, x400).
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F1
The specimen consisted of 16 LNs with metastatic follicular thyroid lesions showing no definite nuclear features of PTC (Fig. 1A). Immunohistochemistry for CK19 (DAKO, Glostrup, Denmark) and Galectin-3 (NOVOCASTRA, Newcastle, UK) were done, and although their results were not supportive (Fig. 1B), the LN were diagnosed as metastatic PTC, considering the metastatic pattern. Another seven years later, he developed a mass in the left thyroid, which was diagnosed as encapsulated FVPTC without capsular or vascular invasion (Fig. 1C), and metastatic LNs displaying same histology as the second presentation (Fig. 1F). However, immunohistochemistry for CD56 (ZYMED, South San Francisco, CA, USA) revealed loss of expression in the follicular cells, rendering the diagnosis of FVPTC (Fig. 1D and E). PTC in the LNs was the same as that of FVPTC (Fig. 1G and H). Preoperative thyroglobulin level was 321.85 ng/mL, which dropped to 185.82 ng/mL postoperatively (Table 1). Six months later, due to radiologically suspicious metastatic lesion in the frontal bone and left 5th rib with thyroglobulin level of 460.0 ng/mL, the patient underwent surgical removal of the skull lesion, diagnosed as metastatic FVPTC (Fig. 1I, J, and K) and received additional RAI 200 mCi treatment.