Langerhans Cell Histiocytosis or Acute Cellular Rejection?

ABSTRACT Background Langerhans cell histiocytosis (LCH) is a rare malignant disorder of epidermal antigen presenting cells. It is characterized by infiltration of various tissues with dendritic cells (Langerhans cells, LC) that express CD1a or CD207 (langerin), often leading to organ dysfunction. A patient with LCH required liver transplantation (LT) for LCH‐associated biliary‐tract disease. Cholangiopathy developed after LT. The question arose: In this patient, did LC in damaged liver‐allograft biliary epithelium signify acute cellular rejection (ACR) or recurrent LCH? Methods We evaluated immunohistochemical identification of LC (CD1a, CD207) in the proposita and in 14 ACR patient samples as distinguishing between ACR and recurrent LCH. Results Among 15 patient samples, 3 (20%) marked with neither antibody. Among the remaining 12 samples (80%), 4 (26.7%)—including that from the proposita—had cells marking for both antigens within bile‐duct epithelium as well as in surrounding portal‐tract connective tissue, 2 (13.3%) had cells marking for both antigens in one region or the other, but not in both, and 6 (40%) had cells marking for only one antigen in one region or the other. Conclusions Immunostaining for CD1a and CD207/langerin in the setting of ACR without suspicion of LCH identifies LC in damaged bile ducts. This biomarker pairing proved not to be LCH‐specific. Our findings indicate that the presence of these cells alone is insufficient to identify recurrent LCH in the allograft liver.