TTF1 and neoplasm: Notably, the tumor was negative for estrogen receptor (ER), thyroid transcription factor 1 (TTF-1), cytokeratin 20 (CK20), and high risk human papillomavirus ribonucleic acid in situ hybridization (HR HPV RNA ISH), and therefore did not support tumor origin of breast or gynecologic, lung, lower gastrointestinal, or cervical or head/neck, respectively.