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(Figure 2). Scattered neutrophils, eosinophils and extravasated red blood cells were also present in the background. On immunohistochemistry, the small histiocytes strongly stained with CD1a and langerin while the MGCs were variably positive for CD1a and negative for langerin. The morphology and immunophenotype was most consistent with LCH, which in this clinical context favored a diagnosis of CSHRH. First reported by Hashimoto and Pritzker in 1973, CSHRH is a benign, cutaneous, self-regressing variant of LCH characterized by single or multiple red-purple or brown papulonodules present at birth or soon thereafter. However, cutaneous LCH can also be an early manifestation of disseminated disease, and it can be difficult to predict at presentation which patients will experience spontaneous involution of their lesions. On histopathology, CSHRH and disseminated LCH with cutaneous involvement appear similar. Lesions from both groups of patients can exhibit epidermal ulceration, necrosis and/or dystrophic calcification, although necrosis may be more common in CSHRH. Both contain variable numbers of eosinophils, foamy cells, multinucleated tumor cells and osteoclast-like MGCs, and both have similar CD1a, S-100, Ki-67 and PHH3 staining patterns. While osteoclast-like MGCs have no known prognostic significance in LCH, it is important that dermatopathologists recognize this histopathologic feature for diagnostic purposes as an abundance of osteoclast-like MGCs may mask the classic histocytic cells of LCH. Especially in young children, LCH should be included in the differential diagnosis of skin tumors containing osteoclast-like MGCs such that these samples can be evaluated using the appropriate immunohistochemical stains. Tina Ho PhD Jennifer Oliver-Krasinski MD Pierre Russo MD Jesse Taylor MD Jenna Streicher MD Adam I. Rubin MD Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania Department of Pathology and Laboratory Medicine, Children’s Hospital of Philadelphia, Philadelphia, Pennsylvania Department of Plastic and Reconstructive Surgery, Children’s Hospital of Philadelphia, Philadelphia, Pennsylvania Department of Pediatrics, Section of Dermatology, Children’s Hospital of Philadelphia, Philadelphia, Pennsylvania Email: [email protected] DOI 10.1111/cup.12954