Abstract

A 44-year-old male with a history of acute myeloid leukemia (AML) in remission several months after chemotherapy developed friable and enlarging lesions on his ear and scalp associated with lab abnormalities and splenomegaly consistent with hemophagocytic lymphohistiocytosis (HLH). Skin biopsy demonstrated a diffuse infiltrate of a medium to large monomorphic population of atypical cells with a high nuclear-to-cytoplasm ratio, irregular nuclear membranes, grooved nuclei, and a moderate amount of eosinophilic cytoplasm. Abundant mitosis and apoptotic bodies with occasional hemophagocytosis were also identified, along with occasional eosinophils. Immunohistochemistry revealed CD1a and S100 positivity in the atypical cells, consistent with Langerhans cell histiocytosis (LCH). Additional stains for BRAF V600E, CD34, and myeloperoxidase were negative. Bone marrow biopsy was negative for recurrent leukemia. He was treated with dexamethasone, etoposide, cytarabine, and ruxolitinib for HLH. While his bone marrow remained negative for leukemia, he ultimately underwent an allogeneic stem cell transplant with complete remission of his AML and LCH. LCH has been reported in association with many solid tumors, lymphoma, leukemias, and myeloproliferative disorders, including AML. Most commonly, LCH has been reported prior to or concurrently with AML diagnosis. The relationship between LCH and AML remains unclear. A similar case of a patient with concurrent LCH and AML with common driver mutations supports a theory of a common clonal origin for these two disorders and raises the possibility that LCH may be best classified as a myeloid/myeloproliferative malignancy. Additional studies are needed to continue to understand this relationship.