Fig. 1

Cytological, macroscopic and histological illustrations of case 1. a Cytological preparation from the thyroid lesion at ×1000 magnification depicting thyrocytes with large, irregular nuclei with suggestive nuclear marginalization in subsets of cells. No clear-cut signet ring cell phenotype was evident. b Macroscopic view of a coronary section through the thyroid lesion, visualizing a 38 mm encapsulated tumor with a tan cut surface, focal hemorrhages and a central cystic clearing. c H&E staining of the thyroid tumor at × 400 magnification, portraying thyrocytes with cytoplasmic vacuolization and nuclear marginalization (signet ring cell appearance) in the majority of tumor cells. d Representative focus depicting capsular invasion, marked with an arrowhead, × 100 magnification. e-g Immunohistochemical analyses at × 400 magnification; TTF1 nuclear stain (e), PAX8 nuclear stain (f), thyroglobulin cytoplasmic stain, including subsets of vacuoles (g). h: Histochemical PAS stain at × 400 magnification, note how the cytoplasmic vacuoles stain negative