Thyroid Transcription Factor-1 is a Specific Marker of Benign but Not Malignant Feline Lung Tumours

Feline lung tumours are currently subclassified according to the criteria of the World Health Organisation, but this scheme contains overlap in the tumour phenotype. The aims of the present study were to re-evaluate the histological features of feline lung tumours and to correlate these with expression of the markers thyroid transcription factor (TTF)-1 and Ki67. TTF-1 was found to be a highly specific marker for neoplastic and non-neoplastic lung tissue and thyroid tissue, but was expressed only weakly in invasive lung tumours. A combined semiquantitative score for Ki67 and TTF-1 expression correlated well with differentiation and invasive behaviour of the tumours and may thus be of potential value for evaluation of feline lung tumours.