{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,10,11]],"date-time":"2025-10-11T02:15:40Z","timestamp":1760148940645,"version":"build-2065373602"},"reference-count":30,"publisher":"MDPI AG","issue":"6","license":[{"start":{"date-parts":[[2023,6,12]],"date-time":"2023-06-12T00:00:00Z","timestamp":1686528000000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Genes"],"abstract":"<jats:p>Programmed death-ligand 1 (PD-L1) is the primary ligand of the receptor programmed death-1 (PD-1) which is constitutively expressed or activated in myeloid, lymphoid (T, B and NK), normal epithelial cells, and cancer. The PD-1\/PD-L1 interaction is crucial for the physiological development of immunological tolerance but also in the development of the cancer. Among these, malignant melanoma represents a tumour in which the immunohistochemical expression of PD-L1 is important to guide future therapeutic choices based on the presence\/absence of expression. Various clones have been used over time for immunohistochemical determination, and different results and heterogeneity remain among the various studies in the literature. We perform a narrative review of the present studies in order to discuss and take stock of what certain achievements have been made in this field, what challenges remain, and what possible solutions can be found.<\/jats:p>","DOI":"10.3390\/genes14061252","type":"journal-article","created":{"date-parts":[[2023,6,12]],"date-time":"2023-06-12T01:28:21Z","timestamp":1686533301000},"page":"1252","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":2,"title":["Immunohistochemical Expression of Programmed Cell Death Ligand 1 (PD-L1) in Human Cutaneous Malignant Melanoma: A Narrative Review with Historical Perspectives"],"prefix":"10.3390","volume":"14","author":[{"ORCID":"https:\/\/orcid.org\/0000-0003-0325-4316","authenticated-orcid":false,"given":"Gerardo","family":"Cazzato","sequence":"first","affiliation":[{"name":"Section of Molecular Pathology, Department of Precision and Regenerative Medicine and Ionian Area (DiMePRe-J), University of Bari, 70124 Bari, Italy"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-0860-3044","authenticated-orcid":false,"given":"Teresa","family":"Lettini","sequence":"additional","affiliation":[{"name":"Section of Molecular Pathology, Department of Precision and Regenerative Medicine and Ionian Area (DiMePRe-J), University of Bari, 70124 Bari, Italy"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-4676-0761","authenticated-orcid":false,"given":"Anna","family":"Colagrande","sequence":"additional","affiliation":[{"name":"Section of Molecular Pathology, Department of Precision and Regenerative Medicine and Ionian Area (DiMePRe-J), University of Bari, 70124 Bari, Italy"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-2882-025X","authenticated-orcid":false,"given":"Irma","family":"Trilli","sequence":"additional","affiliation":[{"name":"Odontomatostologic Clinic, Department of Innovative Technologies in Medicine and Dentistry, University of Chieti, 66100 Chieti, Italy"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-5718-7003","authenticated-orcid":false,"given":"Francesca","family":"Ambrogio","sequence":"additional","affiliation":[{"name":"Section of Dermatology and Venereology, Department of Precision and Regenerative Medicine and Ionian Area (DiMePRe-J), University of Bari, 70124 Bari, Italy"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-5074-4951","authenticated-orcid":false,"given":"Carmelo","family":"Laface","sequence":"additional","affiliation":[{"name":"Medical Oncology, Dario Camberlingo Hospital, 72021 Francavilla Fontana, BR, Italy"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-0591-6723","authenticated-orcid":false,"given":"Paola","family":"Parente","sequence":"additional","affiliation":[{"name":"Pathology Unit, Fondazione IRCCS Ospedale Casa Sollievo della Sofferenza, 71013 San Giovanni Rotondo, FG, Italy"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-0472-5338","authenticated-orcid":false,"given":"Eugenio","family":"Maiorano","sequence":"additional","affiliation":[{"name":"Section of Molecular Pathology, Department of Precision and Regenerative Medicine and Ionian Area (DiMePRe-J), University of Bari, 70124 Bari, Italy"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-4792-3545","authenticated-orcid":false,"given":"Giuseppe","family":"Ingravallo","sequence":"additional","affiliation":[{"name":"Section of Molecular Pathology, Department of Precision and Regenerative Medicine and Ionian Area (DiMePRe-J), University of Bari, 70124 Bari, Italy"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2023,6,12]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"k3529","DOI":"10.1136\/bmj.k3529","article-title":"Efficacy of PD-1 or PD-L1 inhibitors and PD-L1 expression status in cancer: Meta-analysis","volume":"362","author":"Shen","year":"2018","journal-title":"BMJ"},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"434","DOI":"10.1016\/j.immuni.2018.03.014","article-title":"Regulation and Function of the PD-L1 Checkpoint","volume":"48","author":"Sun","year":"2018","journal-title":"Immunity"},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"305","DOI":"10.1186\/s40425-019-0770-2","article-title":"Mechanisms regulating PD-L1 expression on tumor and immune cells","volume":"7","author":"Chen","year":"2019","journal-title":"J. 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