Morphology and immunohistochemistry of true histiocytic lymphoma--report of 4 cases

True histiocytic lymphoma (THL) is a rare malignancy of histiocyte. It is difficult to diagnose by light microscopy alone. In this paper, 4 cases of THL were reported basing on light and electron microscopic examination, and immunohistochemical study. Histiocytic lymphoma was of Langerhans cell origin in one case and of interdigitating reticulum cell origin in the other. The other 2 patients probably belonged to neoplasm of macrophage or dendritic reticulum cell origin. The differential diagnosis between the true histiocytic lymphoma and other tumors or diseases was briefly discussed.