SOX9 and CK15 stem cell markers in canine sebaceous lesions.

Introduction: Sebaceous glands are specialized cutaneous adnexal glands, which work under constant hormonal control to produce sebum. They represent a source of adult stem cells that are located in the reserve cell layer. They can give rise to several proliferative lesions and neoplasms (i.e. adenoma, epithelioma and carcinoma). Ck15 and Sox9 represent two stem cell markers, expressed by the adult stem cells of human sebaceous glands, and are expressed in several human sebaceous tumours. Materials and Methods: The aim of the present study was to investigate the immunohistochemical patterns and levels of expression of Ck15 and Sox9 in a set of canine sebaceous gland lesions. Results: Few scattered Ck15-positive cells, but no Sox9 immunolabelling was observed in the reserve cell layer of normal glands. Sox9 was expressed selectively in the nuclei of the innermost cell layer of the outer root sheath of normal canine hair follicles. The spectrum of canine sebaceous tumours, from benign to malignant, contained a subpopulation of cells expressing Ck15, while Sox9 was expressed only in malignant sebaceous tumours. Conclusions: Although further studies are needed, Ck15+ and Sox9+ cells, having some features of stem cells, may play a role in sebaceous tumour development and progression.