It is likely that a significant number of cases of THL will continue to be misdiagnosed unless appropriate cytochemical and immunologic markers are incorporated into the panel of studies performed at diagnosis. The clinical findings are nonspecific. With the possible exception of skin infiltration, the frequency of symptoms and signs appear to approximate those of intermediate grade lymphomas. Most commonly, it is the histopathological features that suggest the histiocytic nature of a malignant process, but these alone are not sufficient to secure the diagnosis. Thus, in the absence of a clearly defined lymphoid origin, it is the detection of specific histiocytic markers that establishes a lymphoma as THL. Only the recognition and careful study of additional cases will potentially enable clinical investigators to identify any unique characteristics and distinguish this disease from other lymphomas. For the present, it would appear that the treatment indicated for a patient with diffuse large cell lymphoma would also be appropriate for a comparable patient with THL. Although long-term disease-free survival in THL is possible, there are presently inadequate data to estimate curability.