Short Communications: Basic scienceDistinguishing melanophages from tumor in melanoma patients treated with talimogene laherparepvecAudrey-Bayan, Clairea,,*; Trager, Megan H.b,,*; Gartrell-Corrado, Robyn D.c; Rizk, Emanuelle M.d; Pradhan, Jayaf; Silverman, Andrew M.c; Lopez, Adrianae; Marks, Douglas K.g; Niedt, Georgeh; Geskin, Larisa J.b,,*; Saenger, Yvonne M.d,,*Author Information aDepartment of Medicine and Dermatology, University of Minnesota, Minneapolis, Minnesota bDepartment of Dermatology cDepartment of Pediatrics, Division of Pediatric Hematology/Oncology dDepartment of Medicine, Division of Hematology/Oncology, Columbia University Irving Medical Center eDepartment of Medicine, Memorial Sloan Kettering Cancer Center fDepartment of Pathology, Columbia University Irving Medical Center gDepartment of Medicine, New York University, Langone Health hDepartment of Dermatopathology, Columbia University Irving Medical Center, New York, New York, USA *Claire Audrey-Bayan, Megan H. Trager, Larisa Geskin and Yvonne Saenger contributed equally to the writing of this manuscript. Received 3 December 2019 Accepted 4 February 2020 Supplemental Digital Content is available for this article. Direct URL citations appear in the printed text and are provided in the HTML and PDF versions of this article on the journal's website, www.melanomaresearch.com. Correspondence to Yvonne M. Saenger, MD, Division of Hematology/Oncology, Department of Medicine, Columbia University Irving Medical Center, Herbert Irving Pavilion, 161 Fort Washington Avenue, New York, NY 10032, USA, Tel: +1 646 425 5734; fax: +1 212 305 6891; e-mail: firstname.lastname@example.org Melanoma Research: August 2020 - Volume 30 - Issue 4 - p 410-415 doi: 10.1097/CMR.0000000000000661 Buy SDC Metrics Abstract Response to talimogene laherparepvec (T-Vec) is difficult to assess as pigmented macrophages that have ingested melanoma cells (‘melanophages’) persist after injection, mimicking melanoma. We used quantitative immunofluorescence (qIF) to (1) distinguish melanophages from melanoma in biopsies from two patients treated with T-Vec and (2) evaluate the tumor microenvironment pretreatment and posttreatment. Tissues were stained with 4’,6-diamidino-2-phenylindole, cluster of differentiation (CD) 3, CD8, CD68, human leukocyte antigen-DR isotype (HLA-DR), and SRY-Box Transcription Factor 10 (SOX10), and multispectral images were analyzed. Post-T-Vec samples showed melanophages with cytoplasmic costaining of CD68, SOX10, and HLA-DR, without nuclear SOX10 expression. qIF revealed a dense immune infiltrate of CD3+, CD8+, and CD68+ cells in post-T-Vec samples. Melanophages from tumors post-T-Vec stain the nuclear melanoma marker SOX10 in their cytoplasms as compared to melanoma cells that stain nuclear SOX10. This novel finding highlights the phagocytosis of melanoma cell components by macrophages after treatment with T-Vec. qIF may assist pathologists in determining whether lesions treated with immunotherapy contain residual viable melanoma. Copyright © 2020 Wolters Kluwer Health, Inc. All rights reserved.