LAUSR

Immunotherapy with PD-1/PD-L1 axis blockers by inhibiting the binding of PD-1 with its ligands has become an important strategy in advanced melanoma. There is an objective response in 50% of patients with melanoma metastases, and the expression of PD-L1 is associated with a better outcome, but as a sole biomarker, it can be unreliable. Patients presenting PD-L1-negative metastatic melanomas can also respond to PD-1/PD-L1 axis blockers. B lymphocytes, identified by the presence of CD20 in their membrane, began to be studied more recently in the context of melanomas as a potential biomarker in the monitoring and prognosis of patients. The objective of this retrospective cohort study was to analyse the expression of PD-L1 and CD20 in melanoma metastases, according to site, clinical and histopathological data, and survival. We assessed 50 metastatic melanomas in 46 patients. PD-L1 IHC was performed, utilising E1L3N (R), clone (Cell Signaling Technology – Fig. 1a). We graduated the percentage of PD-L1 in melanoma metastases as negative for cases < 5% of tumour cells, and positive in three subcategories: 5–20%, 21–60%, and >60% of tumours cells expressing PD-L1. For the CD20 study, a similar immunohistochemistry technique was utilised using the clone L26 and the diaminobenzidine chromogen (both from Ventana, AZ, USA, Fig. 1b). CD20-positive cases were subclassified as intratumoral and/or peritumoral. To be classified as positive, CD20 lymphocytes should be intratumoral (within the melanoma bulk) and/or peritumoral (around the melanoma bulk, in close contact with its tumour cells). In the study of lymph nodes, cases in which the only location of the CD20 was in follicular centres (their natural location) were considered negative. Table 1 correlates the histopathological data of metastatic and primary melanomas with the expression of PDL1 in metastases. Of the 50 cases analysed, 22 (43%) were positive with expression between 5 and 60% of the cells. The age of the individuals ranged from 29 to 96 years (mean = 62 years). The majority were over 50 years old (37/46). The most frequent skin phototypes were II and III. We did not find a statistical difference between the expression of PD-L1 in metastases and the variables ‘gender’, ‘age’ or ‘phototype’. Patient survival was not associated with the presence of PD-L1. Previous studies assessing survival and PD-L1 expression are contradictory: some relate better prognosis and longer disease-free time, and others, a worse prognosis and less relapse-free time. We