ABSTRACT
Context: Nidogen-2 (NID-2) hypermethylation has been implicated in many types of cancers, such as lung, bladder, and gastric carcinomas. However, its role has not yet been studied adequately in head and neck squamous cell carcinomas (HNSCC). HNSCCs constituting a major portion of the global cancer load, it is of importance to diagnose and treat them at earliest. This systematic review was performed to assess the role of NID-2 in HNSCCs and assess its utility as a diagnostic and prognostic marker. Materials and Methods: A systematic search was performed across multiple databases to identify studies pertaining to analysis of expression or methylation of NID-2 in HNSCCs. The sample size, type of cancer/premalignant condition studied, type of tissue/fluid analysed, and the various methodologies used and their results were extracted. PROSPERO registration number: CRD42021245326. Results: Four studies were identified after a systematic search of literature. The studies analysed NID-2 expression or methylation in conditions such as nasopharyngeal carcinoma, esophageal carcinoma, and oral squamous cell carcinoma (OSCC). NID-2 was found to be a highly specific marker for HNSCCs, and serum NID-2 levels also correlated with poor survival. Conclusion: Data from the reviewed studies indicate that hypermethylation of NID-2 is highly specific for HNSCC. The high specificity is maintained in salivary and serum samples, facilitating accurate and non-invasive prognostication of HNSCC. The relatively lower sensitivity of NID-2 methylation may be overcome by analysing it along with a panel of multiple biomarkers such as HOX-A2 and YKL20.
ABSTRACT
The objective of this review is to introduce Merkel cells (MCs), to provide a basic overview on the theoretical background of function, development and clinical importance of MCs. The origin of human MCs have been controversial. Some investigators believe that it is a neural crest derivate, whereas others have proposed that it is a differentiation product of the fetal epidermal keratinocytes. MCs are cells primarily localized in the epidermal basal layer of vertebrates and concentrated in touch-sensitive areas in glabrous, hairy skin and in some mucosa. In routine light microscopy, human MCs can hardly be identified. Cytokeratin 20 (CK20) is a reliable marker with highest degree of specificity. MCs can be also distinguished by electron microscopy. MC carcinoma (MCC) is an uncommon and often aggressive malignancy and found mainly in elderly patients. It occurs most frequently in the head and neck region. Diagnosis is based on typical histological presentation on hematoxylin and eosin (H and E) stained slides together with the results of immunohistochemistry. Histologically, MCC has been classified into three distinct subtypes: Trabecular, intermediate and small cell type.