Fig. 3
Haematoxylin/eosin and KRT19 expression in lung primary tumours. a Small cell carcinoma. Only isolated cells are positive for KRT19 (˂1%; red arrows). b Large cell carcinoma. Heterogeneous immunostaining with a positive pattern of ˃ 10% of tumour cells (red arrows). c Large cell carcinoma. Heterogeneous expression of numerous neoplastic cells with different levels of expression (black and yellow arrows), although obvious in all of them. d Mixed neuroendocrine carcinoma. Differential expression between the two components of the neoplasm: weak and patchy in the small cell (green arrow) and intense and diffuse in the large cell component (blue arrow). e Lymphoepithelioma-like carcinoma. Neoplastic cells show a faint and heterogeneous pattern (black arrows) although some elements show high expression of KRT19 (yellow arrows). f Pleomorphic carcinoma. Intense immunostaining in the glandular component (green arrow) and heterogeneous pattern of less intensity in the sarcomatoid fraction (blue arrow). g Adenocarcinoma. Heterogeneous but obvious pattern of expression of KRT19 (black and yellow arrows). h Adenocarcinoma. Intense and diffuse positivity for KRT19 in the whole tumour. i Squamous cell carcinoma. High expression of KRT19 in all tumour cells. Objective magnification ×10