To highlight the most characteristic histopathological findings of oral lichen planus and their correlation with the clinical manifestations and forms. We performed a retrospective study of 50 biopsied and diagnosed cases of oral lichen planus obtained over a period of 11 years, spanning from May 1998 to April 2009. We analyzed the age and sex of the patient, type of lichen planus, location and different histopathological findings, comparing them with the clinical lesions. Seventy eight percent of the patients are female and 22% are male, with an average age of 56.06 years for both sexes. The most frequent clinical form is reticular, present in 78% of the cases, and the most common location is the buccal mucosa, present in 70% of the patients. Hydropic degeneration of the basal layer and lymphocytic infiltration in the subepithelial layer are observed in the entire sample. Signs of atypia were identified in 4% of the cases, but without dysplasic features. Other common histological findings were the presence of necrotic keratinocytes (92%), hyperplasia (54%), hyperkeratosis (66%), acanthosis (48%), and less frequently, serrated ridges (30%) and the presence plasma cells (26%). Oral lichen planus is a disease that is more common in women, usually appearing in the fifth and sixth decades of life. The most common clinical form is reticular, manifesting mainly in the buccal mucosa. Histological findings characteristic of oral lichen planus include hydropic degeneration of the basal layer, lymphocytic infiltration in the subepithelial layer and the absence of epithelial dysplasia; however, it is also frequent to observe hyperplasia phenomena at the epithelial level, hyperkeratosis, acanthosis and the presence of necrotic keratinocytes.

Acidity is one of the main characteristics of OSCC (oral squamous cell carcinoma) as a solid tumor. The V-ATPase is the primary regulator of the tumor microenvironment, by means of proton extrusion to the extracellular medium. The decrease in extracellular pH confers the cells a resistant, highly invasive and metastatic phenotype. However, the acid medium confers an optimum pH to the degradative enzymes (such as proteases and MMPs) for their proper functioning. The C subunit (ATP6V1C) of V1 intra-membrane domain of the V-ATPase, is primarily responsible for its enzymatic function, through the control of a reversible dissociation of V0 and V1 domains. In this review, we describe the importance of V-ATPases in the control of tumor microenvironment, the potential strategies as protein targeting to improve the effectiveness of drug treatment and the role of the C subunit as the primarily responsible of the enzymatic control. The inhibition of the V-ATPase activity through PPIs (proton inhibitors) seems to reduce the destructive and metastatic capacity in tumors, such as hepatocellular carcinoma. Nevertheless, none of these inhibitors was proven to be useful in OSCC; therefore, it is highly important to carry out further studies in order to develop specific inhibitors of the C subunit, to control the devastating effects of OSCC.