Fig. 3. Primary thyroid secretory carcinoma with ETV6-NTRK3 fusion (case 11).
The tumor demonstrated a lobulated appearance with prominent intratumoral fibrosis (a). Admixed microcystic and tubulopapillary patterns were seen, and the cells showed elongated, often grooved nuclei with finely speckled chromatin and central nucleoli (b, inset). The cytoplasm was abundant and vacuolar, frequently containing intracytoplasmic eosinophilic globules in a signet ring-like appearance (b, inset). By immunohistochemistry, there was diffuse expression of mammaglobin (c) and S100 (d), and focal weak TTF1 (e). PAX8 was negative (f).