Fig. 1

Photomicrographs demonstrating histological and immunohistochemical attributes of the primary and metastatic lesions. Magnification set to × 100 if not otherwise specified. A Routine hematoxylin–eosin (H&E) stain at × 200 magnification depicting the primary papillary thyroid carcinoma built-up by tumor cells with a predominantly papillary architecture. B Same tumor at × 400 magnification, displaying the classical nuclear features of PTC; nuclear elongation and crowding, chromatin clearing and nuclear membrane aberrancies (nuclear folds, pseudoinclusions). C Widespread CK19 immunoreactivity was noted within the primary tumor. D Strong and diffuse MET expression in the primary PTC (top) with negative staining in the normal thyroid parenchyma (bottom). E Routine H&E section of the lymph node metastasis with a horizontal line for clarity, a conventional PTC metastasis is visible (bottom) adjacent to an area exhibiting features of poorly differentiated thyroid carcinoma (PDTC, top). F Two inserts at × 400 magnification; bottom row depicts the metastatic PTC with its associated nuclear hallmarks, while the top row highlights key findings of the PDTC component, compact growth pattern, mitoses and absence of PTC-associated nuclear features. G-L Immunohistochemical analyses comparing expression in the metastatic PTC (bottom) with the metastatic PDTC (top) using the following markers; CK19 (G), MET (H), PAX8 (I), CK7 (J), TTF1 (K) and Ki-67 (L). Note how both metastatic components exhibit strong MET immunoreactivity