TTF1 and thyroid tumor: Thyroblastoma is an embryonal high-grade triphasic thyroid neoplasm composed of (1) primitive thyroid epithelium (positive for thyroglobulin, TTF1, and PAX8), (2) a blastemal component of small cells positive for SALL-4, and (3) a spindle cell stroma usually positive for alpha-smooth muscle actin, desmin, and myogenin [8, 26].