TTF1 and neoplasm: TTF‐1 immunostaining was repeated using a different clone of the monoclonal antibody against TTF‐1 (mouse monoclonal, clone 8G7G3/1; Cell Marque, Rocklin, CA, USA; 1:200); tumor cells were again negative, whereas nuclear positivity was present in the neoplastic cells of a brain metastasis of lung adenocarcinoma used as positive control (Fig. 3).