Altered expression of collagen XVII in ameloblastomas and basal cell carcinomas

: Background: Collagen XVII (BP180) is an epithelial transmembrane protein, which presumably plays a role in cell migration and differentiation under both physiological and pathological conditions. Ameloblastoma, the most common odontogenic neoplasm, and basal cell carcinoma (BCC) of the skin exhibit similar growth patterns and share histological features. Methods: Here, we examined the distribution and expression of collagen XVII in ameloblastomas and BCCs using immunohistochemistry and non‐radioactive in situ hybridization. In both tumors, the distribution of collagen XVII varied in different parts of the lesions. Results: In ameloblastomas, immunostaining for collagen XVII was usually localized in the basal and suprabasal cells of the tumor nests, although in some tumors, a diffuse intracellular staining was detected in the central cells of the neoplastic islands. In BCCs, collagen XVII was mostly seen as diffuse cytoplasmic staining in some central and peripheral cells of the tumor islands and also at the cell membranes in the basal keratinocytes of the epidermis overlying the tumor nests. Double immunostaining with antibody against γ2 chain of laminin‐5 showed that these two components of the keratinocyte adhesion complex are usually co‐localized in ameloblastomas and BCCs. In both tumors, collagen XVII mRNA was found in the basal epithelial cells and in some central and peripheral cells of the tumor islands, while the stromal cells were negative. Conclusions: These findings indicate that the expression of collagen XVII may be differentially regulated in various parts of the tumor. Diffuse intracellular distribution of collagen XVII and a consequent loss of critical cellular attachments may contribute to the infiltrative and progressive growing potential of tumors.