The Hammersmith Hospital hematopathology case of the month: myeloid sarcoma with Langerhans cell proliferation.

We present a patient whose initial lymph node biopsy showed extensive histiocyte and Langerhans cell infiltration, which obscured the underlying myeloid sarcoma (MS). The initial diagnosis of Langerhans cell histiocytosis (LCH) was not compatible with the disease evolution, and a subsequent biopsy performed much later showed all the characteristics of MS. Clinical distinction between LCH and MS involving the skin and management of these diseases, and the reported association of LCH/Langerhans cell proliferations with myeloid and lymphoid malignancies, are discussed.