BACKGROUNDCutaneous squamous cell carcinoma (SCC) is the second most common type of skin cancer. Only 2% to 5% of SCCs metastasize; however, those do carry a poor prognosis. Immunohistochemistry (IHC) is widely used by pathologists to characterize skin cancers and provide clinically useful information.OBJECTIVETo evaluate the potential prognostic associations between IHC findings and metastasis in SCC.METHODSSearches were conducted in MEDLINE via PubMed for articles published between 1999 and 2019. Search criteria included key words "immunohistochemistry"and "cutaneous squamous cell carcinoma."Six hundred and fifty-three articles were returned and screened, which ultimately left 31 for inclusion in our manuscript.RESULTSThirty-one articles analyzed in this review included a discussion of the expression of a particular IHC marker and the associated risk of metastasis and/or clinical utility of IHC markers in SCC, especially metastatic SCC. Markers that had several or more studies supporting clinical utility were E-cadherin, podoplanin, CD8+ T cells, PD-L1, epidermal growth factor receptor, and Cyclin D1.CONCLUSIONImmunohistochemistry profiling of SCC may be useful in select cases when providing a prognosis remains challenging and in identification of potential therapeutic targets for high-risk or metastatic tumors.
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