Expression of CD56 antigen in Langerhans cell histiocytosis associated with T-lymphoblastic lymphoma in a same lymph node

Association of T-lymphoblastic lymphoma (LBL) and Langerhans cell histiocytosis (LCH) in the same lymph node is very rare. Herein, we report such two cases with expression of CD56 in Langerhans cells. Immunohistochemically, lymphoblasts were positive for anti-polyclonal CD3 antibody, CD34, CD7, CD99, and terminal deoxynucleotidyl transferase. LCH cells were positive for anti-S100 protein, CD1a, CD4, CD56, and CD68. Although those two populations were separated topographically, many histiocytes intermingled with lymphoblasts in the paracortex and a few lymphoblasts were scattered within the intrasinusoidal sheets of histiocytes. Neither admixed eosinophils nor multinucleated giant cells were observed. The pathogenetic mechanism of CD56 expression in LCH associated with LBL is discussed.