True Histiocytic Lymphoma: An Immunohistochemical and Ultrastructural Study of Two Cases

Immunologic studies demonstrate that non-Hodgkin’s lymphomas are derived predominantly from B- or T-lymphoid cells, while node-based tumors of true histiocytic derivation are rare, with few documented cases. This report describes the clinical, histologic, immunohistochemical, and ultrastructural features of two cases of node-based true histiocytic lymphoma. Distinctive ultrastructural features included numerous cytoplasmic lysosomes, surface microvillous processes, and occasional cell junctions, and the cells stained strongly for alpha napthyl acetate esterase and alpha one-antitrypsin. Since there are few specific histologic features, special technics may be essential in confirming the diagnosis of true histiocytic lymphoma, and determining appropriate therapy.