Fig. 3

MRI and immunohistochemistry of the oral tissue sample after the tumor recurrence. MRI of head tumour recurrence into the region of the right zygomatic bone growing into the caudal part of the orbit (A). Epithelial cords of tumour compound of columnar cells with reverse polarization, dense cellularity in basal parts of tumour, increased mitotic activity and nuclear hyperchromasia; Haematoxylin–Eosin staining, magnification 200x (B). Diffuse membranous positivity of pan-cytokeratin with maximum of positivity in stellate reticulum-like cells in tumour tissue; immunohistochemistry: CK AE1/AE3 (pan-cytokeratin (1:1, cat. no. 961, Abcam, UK), magnification 200x (C). Weak nuclear immunoreactivity of p53 in tumour cell; immunohistochemistry: p53, magnification 200x (D). Nuclear positivity of Ki67 staining reaches the level up to 10% and represents increased proliferation activity; immunohistochemistry: Ki67 (1:200, cat. no. 275-R-16, Cell Marque, USA), magnification 200x (E). 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