Cutaneous neoplasms are the most common neoplasm in dogs. The transforming growth factor (TGF-b) family has an ambivalent role in cancer progression, as it has been shown to have both tumour-suppressing and tumour-enhancing effects. In this study we aimed to detect TGF-b1 expression in canine spontaneous cutaneous tumours by immunohistochemistry. We examined 16 samples of canine spontaneous cutaneous tumours including: sebaceous gland tumours (3), basal cell tumours (2), transmissible venereal tumours (3), hepatoid gland adenoma (1), trichoblastoma (1), reticular cell carcinoma (1), fibrosarcoma (1), melanoma (1), spindle cell tumour (1), leiomyosarcoma (1), and myxoma (1). These were routinely processed and immunostained with anti-TGF-b1 antibody using the avidin biotin method, horse radish as enzyme reagent, and diaminobenzidine as chromogene. Canine normal skin and mouse ovary tissues were used as negative and positive controls, respectively. Immunoscoring was done according to the distribution of positive cells and intensity of positive signals in comparison with positive control. Slides stained by immunohistochemistry were scored as negative ()), weak (+), moderate (++), and strong (+++). TGF-b1 was variably expressed by the 16 cutaneous tumours in comparison to normal skin. Three tumours showed no specific labelling, five tumours were scored as weakly immunoreactive, five moderately, and three strongly, compared to controls. In summary, we observed that 13 of 16 tumours expressed TGF-b1 to some degree. These data suggest that TGF-b1 may be a potential target for treatment of canine skin tumours. However, more investigation is required to understand its function in cutaneous neoplasms in dogs.

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