Original StudyThree Types of Nodal Melanocytic Nevi in Sentinel Lymph Nodes of Patients With Melanoma: Pitfalls, Immunohistochemistry, and a Review of the LiteratureGonzàlez-Farré, Mònica MD*,†; Ronen, Shira MD†; Keiser, Elizabeth MD†; Prieto, Victor G. MD, PhD†; Aung, Phyu P. MD, PhD†Author Information *Department of Pathology, Hospital del Mar, Barcelona, Spain; and †Department of Pathology, The University of Texas-MD Anderson Cancer Center, Houston, TX. Correspondence: Phyu P. Aung, MD, PhD, Department of Pathology, The University of Texas MD Anderson Cancer Center, 1515 Holcomb Blvd Unit 85, Houston, TX 77030 (e-mail: email@example.com). The authors declare no conflicts of interest. The American Journal of Dermatopathology: October 2020 - Volume 42 - Issue 10 - p 739-744 doi: 10.1097/DAD.0000000000001645 Buy Metrics Abstract The presence or absence of metastasis in sentinel lymph nodes often drives melanoma staging, prognosis, and treatment. However, distinguishing between metastatic melanoma cells and clusters of benign melanocytic nevus cells is not always straightforward. When morphologic hematoxylin and eosin interpretation alone is not sufficient, additional hematoxylin and eosin sections and immunohistochemical (IHC) studies may be beneficial. This review and small cases series of 3 diagnostically challenging melanocytic sentinel lymph node cases highlights the IHC approach to evaluate intraparenchymal nodal melanocytic nevi, coexistent metastatic melanoma with adjacent melanocytic nevi cells, and nodal blue nevi. In challenging cases, cytological morphology of the melanocytes, location within the lymph node, and IHC studies may assist in diagnosis. If these tools yield conflicting results, expert opinion is recommended. Copyright © 2020 Wolters Kluwer Health, Inc. All rights reserved.