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The International Index is a powerful predictor of outcome in the aggressive non-Hodgkin's lymphomas that is based solely on clinical features. Proliferative activity (% S-phase) measured by flow cytometry has been reported to have prognostic significance in many series and may represent a biologic correlate of clinical behavior that further defines prognosis. Flow cytometric analysis of cellular DNA content and proliferative activity (% S-phase) was performed on fixed paraffin-embedded biopsy specimens from 242 previously untreated patients with diffuse, aggressive non-Hodgkin's lymphomas entered on phase III intergroup clinical trials. The International Index was calculated for each patient based on stage, lactate dehydrogenase, performance status, number of extranodal sites, and age, as previously reported. The International Index consistently predicted response to therapy (P = .027) and survival (P = .007) in this series. DNA aneuploidy was shown in 57% of cases, but was not predictive of clinical outcome. The median % S-phase was 9.9 (median coefficient of variation, 3.6%), which was highly correlated with mitotic index (P = .0001). Although a trend associating low proliferative activity with good early survival and very high S-phase with a shortened survival was shown, International Index risk was the only significant predictor of survival in the multivariate analysis. Although proliferative activity quantitated by flow cytometric analysis of nuclei extracted from paraffin-embedded specimens is probably predictive of survival, it is a less powerful prognostic indicator than clinical parameters represented by the International Index and provides no additional prognostic information.

The ETS oncogene family member PU.1 is a transcriptional activator that is dysregulated by Friend erythroleukemia virus insertion. Northern analysis found that PU.1 is highly expressed in cells of myeloid and B-lymphoid origin, but not expressed at all in a number of nonhematopoietic tissues. Interferon-gamma and retinoic acid downregulated PU.1 expression in marrow macrophages. In situ immunohistochemistry found that PU.1 is expressed only in early granulocytic and erythroid cells and megakaryocytes, but not in mature erythroid cells, mature granulocytes, endothelial cells, or osteocytes. Thus, its expression pattern makes PU.1 a candidate for a genetic determinant of lineage commitment and stage progression in blood cell development. It also lends insight into how PU.1 might play a role in Friend virus erythroleukemia.

Epstein-Barr virus (EBV) has been implicated in the pathogenesis of several B-cell lymphoid proliferations. Because patients with hairy cell leukemia (HCL) have a high incidence of seropositivity for EBV antigens, we studied the cells of HCL for evidence of EBV infection using in situ hybridization techniques. EBV mRNA was detected in the tumor cells in four of six cases using a radiolabeled RNA probe. Confirmatory serologic data were available in three cases in which the viral DNA was detected and in one negative case. Our results suggest that EBV infection may have a pathogenetic role in this disorder.

We undertook a study of 35 cases of myelofibrosis with myeloid metaplasia to assess the histopathologic findings in the bone marrow of patients with this disorder, to ascertain if changes in morphology occurred with time, and to attempt to correlate marrow findings with splenic size. We reviewed 71 bone marrow biopsies and studied 13 splenectomy specimens. Sequential bone marrow biopsies were obtained in 21 cases over intervals ranging from two to ten years (mean, 4 1/2 years). We noted a patchy nature and variable degree of stromal proliferation in most marrow biopsies, and were unable to demonstrate a correlation between the extent of medullary fibrosis and duration of disease, splenic weight, or degree of splenic myeloid metaplasia. We were unable to document a progression of medullary fibrosis as a cause for increasing splenomegaly. However, the alteration in the marrow stroma in this disorder is responsible for the presence of distended marrow sinusoids with intravascular hematopoiesis, a phenomenon we observed in all cases. We believe that this morphological feature, not emphasized by previous investigators, is of significance in understanding the pathophysiology of myeloid metaplasia.

This retrospective study of diffuse mixed (DM) cell lymphoma was undertaken as a collaborative study between the Repository Center for Lymphoma Clinical Studies and four cooperative oncology groups (CALGB, ECOG, SECSG, SWOG), and was based on 62 patients from the files of the Repository Center. We wanted to ascertain whether there were any significant clinical differences among the various morphological subtypes of this lymphoma. All patients were treated according to different protocols of the Cooperative Oncology Groups sponsored by the National Cancer Institute. In 16 patients (26%), the malignant lymphoma (ML) had morphological features consistent with follicular center cell origin (FCC); in 34 patients (55%), the ML did not have features of follicular center cell type (non-FCC), but had morphology described for peripheral T-cell-derived ML. In 8 of the patients (13%), no agreement could be reached by the 7 histopathologists who participated in the study, and these were classified as unresolved; the remaining 4 (6%) were unclassifiable. We compared the survival times of the 16 patients having the morphological features of the FCC subtype with the survival times of the 34 patients with the non-FCC subtype and found that patients with FCC lived longer (p = 0.07 Cox's regression). In the FCC group, all patients who had complete remissions (CR) were alive; however, their survival times were similar to those who had a partial or no response (p = 0.32). In contrast, in the non-FCC group, the median survival was 20 mo, and patients with a CR had a significantly longer survival than did incomplete responders (p = 0.003). According to these results the non-FCC diffuse mixed cell lymphoma appears to be a high-grade malignant lymphoma, whereas the FCC type is not.