Bone marrow involvement by CD1a-negative langerhans cell histiocytosis with associated hemophagocytosis

Excerpt

An 80-year old male with multiple liver lesions was diagnosed with Langerhans Cell Histiocytosis (LCH) on liver biopsy. Progressive macrocytic anemia, thrombocytopenia and leukoerythroblastic blood film raised concerns about bone marrow involvement by LCH. A bone marrow aspiration showed increased histiocytes with bilobed nuclei; hemophagocytosis was present in some histiocytes (Fig. 1a–c; objective magnification × 100, May Grunwald-Giemsa stain). Additional clinical and laboratory findings, including elevated ferritin and soluble IL2 receptor supported the diagnosis of hemophagocytic lymphohistiocytosis (HLH). The bone marrow trephine biopsy revealed interstitial clusters of oval-shaped histiocytes, many with bilobed or grooved nuclei, consistent with Langerhans cells. By immunohistochemistry, the cells expressed S100 and unlike the Langerhans cells observed in the liver, these cells were CD1a negative. BRAF V600E immunohistochemical stain displayed variable faint positivity (Fig. 1d–f; objective magnification × 40). Quantitative PCR analysis of the BRAF gene (ABI 7900HT Applied Biosystems) performed on the bone marrow aspirate detected the V600E mutation.

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