Fig. 4

CT and PET CT analysis and immunohistochemistry of the lung metastases. CT of lungs with suspicious signs of tumour in the S3 region of the left lung (A). PET CT confirmed viable tumorous tissue in the S3 region of left lung (B). Epithelial cords located in dense fibrovascular stroma in lung tissue with features including high N/C ratio, increased mitotic figures. These features are suspicious for possible malignant behaviour of tumour, but not fully represent malignancy; Haematoxylin–Eosin staining, magnification 200x (C). Diffuse membranous positivity of pan-cytokeratin with the maximum of positivity in stellate reticulum-like cells of tumour. Immunohistochemistry—CK AE1/AE3 (pan-cytokeratin (1:1, cat. no. 961, Abcam, UK), magnification 200x (D). Nuclear staining of p53 in hot-spots; immunohistochemistry p53, magnification 200x (E). Nuclear positivity of Ki67 staining is increased up to 15–20% in cell-dense hot-spots and represents increased proliferation activity of the tissue; immunohistochemistry Ki67 (1:200, cat. no. 275-R-16, Cell Marque, USA), magnification 200x (F). 3,3′-diaminobenzidine (DAB, cat. No. K3468, DAKO, Agilent Technologies, USA) was used to detect the positive cells and Haematoxylin was applied to counterstain the nuclei