Melanoma is the most aggressive among all skin cancers and is responsible for a high mortality rate. Combined immunotherapies have demonstrated greater efficacy in boosting the immune system of melanoma patients. However, the clinical decision on which combination to be used and which patients will benefit the most from it remains a challenge. Understanding the immune context of patients’ tumor and the identification of reliable biomarker readouts will assist clinicians in their decision. We developed a multiplex immunohistochemistry assay to profile the tumor microenvironment of metastatic melanoma patients who responded or who did not respond to combined immunotherapy. We used LabSat®, an automated stainer based on Lunaphore’s microfluidic technology, to analyze the expression of PD-L1, CD8, and LAG-3. Our results provide first-time evidence of a different expression pattern of these markers between responder and non-responder melanoma patients.