PAX8 and neoplasm: Immunohistochemistry revealed tumor cells to be diffusely positive for cytokeratin 7 (CK7) and CK19 (Figure 1C and 1D) and negative for CK20, thyroid transcription factor (TTF-1), Gross Cystic Disease Fluid Protein-15 (GCDFP-15), mammaglobin, Hepatocyte Paraffin 1 (Hep Par1), Paired box gene 8 (PAX-8) and Wilms tumor gene 1 (WT1).