Bone marrow involvement in large-cell lymphoma. Prognostic implications of discordant disease

Discordant lymphomas are those in which two different histologic subtypes of non-Hodgkin's lymphoma are present simultaneously in the same patient at two or more separate disease sites. Discordance usually involves a lower grade follicular lymphoma in one anatomic site and a higher grade diffuse lesion elsewhere. A common type of discordance is seen in patients with a primary diagnosis of diffuse large-cell lymphoma (DLCL) who demonstrate bone marrow involvement by a lower grade lesion, such as a small cleaved cell or mixed small cleaved and large cell lymphoma. This study was undertaken to assess retrospectively the clinical implications of such bone marrow involvement, as well as the possible biologic mechanisms. Of the 59 DLCL cases studied, 20 (33.9%) showed evidence of bone marrow involvement, 14 of which were discordant (70%). The most significant findings included the following: Overall treatment responses and survivals in discordant patients with predominantly small cleaved cells in the marrow were similar to those in patients with no marrow involvement (mean survivals, 47.7 and 49 months, respectively), and were significantly longer than in patients with concordant marrow involvement (mean survival, 13.1 months, P < .05). Patients with discordant marrow infiltrates composed of a mixed cell population tended to do as poorly as those with concordant involvement. No clear-cut pattern of relapse in discordant patients was found, but persistence of small cleaved cells in some was reminiscent of lower grade B-cell lesions. Other features associated with lower grade lesions included older age, less incidence of central nervous system involvement, and lesser extent and proportion of marrow infiltration. Finally, in approximately half the cases with discordant involvement, lymphoma was present unilaterally, emphasizing the need to perform bilateral biopsies for staging.