Canine hair follicle stem cells have been identified in a specialized area of the outer root sheath. The increasing interest in the characterization of these cells is also related to the key role they may play in the onset of tumours. Survivin has yet been identified as hematopoietic, mesenchymal, intestinal and interfollicular epidermis stem cells marker. Its overexpression has been found in several human and canine cutaneous tumors, suggesting a possible involvement of the molecule in tumour initiation and cancer stem cell maintenance. The immunohistochemical expression of survivin was evaluated in 4 normal skin samples and 30 hair follicle tumours of dog, with a comparison with the expression of known stem cell markers, in order to establish its possible role as a marker of follicular and cancer stem cells. Positive nuclei were observed in scattered cells of the basal cell layer of normal epidermis and among basal cells of the outer root sheath and matrical cells of the hair follicle bulb. The highest number of positive cells were present in trichoblastomas and among cells with matrical differentiation of pilomatricomas and trichoepitheliomas. The present results would suggest survivin as a follicular stem cell marker, considering the presence of positive cells in the outer root sheath and its overexpression in tumours deriving from these cells: trichoepitheliomas and trichoblastomas. However, further studies are needed to better define the role of survivin as follicular stem cell marker.[...
