Periorbital melanosis and pigmentary demarcation line of the face are not two different conditions; rather they are two different manifestations of the same disease.
Oral Lichen Planus (OLP) is a relatively common, systemic, immune based disease. It usually, involves the oral mucosa, but other sites like the skin, genital mucosa, and scalp are also affected. In this autocytotoxic muco-cutaneous disease, the T lymphocytes trigger apoptosis of epithelial cells leading to chronic inflammation. OLP is mediated by both antigen specific and nonspecific pathways. Antigen presentation through basal keratinocytes and antigen-specific keratinocyte destruction by CD8+ cytotoxic T-cells are within the specific pathway spectrum. Whilst the nonspecific methods involve mast cell degeneration; leading to granular release and matrix metalloproteinase (MMP) activation. The process ultimately results in clustering of T cells in the upper layer of lamina propria, basal lamina disruption, Tcell inflow within the epithelium, along with apoptotic death of keratinocytes. The normal oral mucosa may be an immune privileged site and breach of the immune barrier could result in OLP and possibly other autoimmune oral mucosal diseases owing to deficient antigen-specific TGF-β1-mediated immunosuppression. However, many among these immuo pathologic mechanisms are still shroud in mystery.
The concept "field effect in cancer" originated in 1953, from the histopathological observations of Slaughter and colleagues regarding the occurrence of multiple primary oral squamous cell carcinomas and their local recurrences. There are two fundamental theories regarding the development of oral field cancerization (OFC) which includes the "classical" and the "clonal" mechanism. The classical view hypothesizes that the entire epithelial surface of the upper aerodigestive tract has an increased risk for the development of premalignant disorders because of multiple genetic abnormalities in the whole tissue region; owing to prolonged exposures of susceptible carcinogens as a result of tobacco or alcohol consumption. While the clonal theory believes that there always exists a field with genetically altered cells having a high risk of developing premalignant and malignant disorders. Here, the developing separate tumors from a genetically individually altered stem cell in the extended field, share the same clonal origin, and some degree of genetic similarity. Modern molecular and histological technologies exploring the tissue abnormalities in OFC have been performed. Herein, we have briefly discussed regarding the concepts of field cancerization along with the various diagnostic molecular techniques and the therapeutic aspects.
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