TTF1 and neoplasm: Immunohistochemical staining was performed in six PSPs, and we found that some tumor cells were immunopositive for epithelial membrane antigen (EMA) (3/6), thyroid transcription factor‐1 (TTF‐1) (6/6), vimentin (2/6), CD68 (2/6) and cytoskeleton 7 (CK‐7) (4/6).