Marginal zone B-cell lymphoma: A clinical comparison of nodal and mucosa-associated lymphoid tissue types. Non-Hodgkin's Lymphoma Classification Project

PURPOSE

In the International Lymphoma Study Group classification of lymphoma, extranodal marginal zone B-cell lymphoma (MZL) of mucosa-associated lymphoid tissue (MALT) type is listed as a distinctive entity. However, nodal MZL is listed as a provisional entity because of questions as to whether it is truly a disease or just an advanced stage of MALT-type MZL. To resolve the issue of whether primary nodal MZL without involvement of mucosal sites exists and whether it is clinically different from extranodal MALT-type lymphoma, we compared the clinical features of these two lymphomas.

PATIENTS AND METHODS

Five expert hematopathologists reached a consensus diagnosis of MZL in 93 patients. Seventy-three were classified as having MALT-type MZL because of involvement of a mucosal site at the time of diagnosis, and 20 were classified as having nodal MZL because of involvement of lymph nodes without involvement of a mucosal site.

RESULTS

A comparison of the clinical features of nodal MZL and MALT-type MZL showed that more patients with nodal MZL presented with advanced-stage disease (71% v 34%; P =. 02), peripheral lymphadenopathy (100% v 8%; P <.001), and para-aortic lymphadenopathy (56% v 14%; P <.001) than those with MALT-type MZL. However, fewer patients with nodal MZL had a large mass (> or = 5 cm) than those with MALT-type MZL (31% v 68%; P =.03). The 5-year overall survival of patients with nodal MZL was lower than that for patients with MALT-type MZL (56% v 81%; P =.09), with a similar result for failure-free survival (28% v 65%; P =.01). Comparisons of patients with International Prognostic Index scores of 0 to 3 showed that those with nodal MZL had lower 5-year overall survival (52% v 88%; P =.025) and failure-free survival (30% v 75%; P =.007) rates than those with MALT-type MZL.

CONCLUSION

Nodal MZL seems to be a distinctive disease entity rather than an advanced stage of MALT-type MZL because the clinical presentations and survival outcomes are different in these two types of MZL. Clinically, nodal MZL is similar to other low-grade, node-based B-cell lymphomas, such as follicular and small lymphocytic lymphomas.

Nodal monocytoid B-cell lymphoma (nodal marginal-zone B-cell lymphoma)

Benign monocytoid B cells are seen in lymph nodes in different types of lymphadenitis and they occur in the form of clusters within and around sinuses and in the interfollicular areas, but rarely completely surround benign follicles to produce a marginal-zone pattern. The cytologic hallmark of these cells is the presence of abundant pale to clear cytoplasm; these cells usually are of medium size, and they have a rather bland-appearing, irregular nuclei with inconspicuous nucleoli. Malignant monocytoid B-cell proliferations in a lymph node have been classified as monocytoid B-cell lymphomas (MBCL), which are now called nodal marginal-zone B-cell lymphoma (MZL) in the World Health Organization (WHO) classification. In the recently published clinical evaluation of the International Lymphoma Study Group classification of non-Hodgkin's lymphoma, 25 of 1,378 cases (1.8%) were classified as primary MZL, whereas four times as many cases (105 or 7.6%) were classified as low-grade mucosa-associated lymphoid tissue (MALT)-type lymphoma. Transformation to large-cell lymphoma at the time of diagnosis was seen in five of 25 (20%) cases of nodal MZL and in 32 of 105 (30%) cases of MALT-type lymphoma. Comparison of the clinical findings at presentation and the survival results indicate that nodal MZL is more aggressive clinically than low-grade MALT-type lymphoma. For example, patients with nodal MZL had a significantly higher incidence of advanced-stage disease, including peripheral and paraaortic lymphadenopathy, than those with MALT-type lymphoma. Moreover, patients with nodal MZL had lower 5-year overall survival and failure-free survival than patients with MALT type lymphoma. When analysis was restricted to those patients with zero to three adverse risk factors in the International Prognostic Index, patients with nodal MZL still had a significantly lower overall and failure-free survival at 5 years than patients with MALT-type lymphoma. We conclude that nodal MZL is a distinctive disease entity and is similar to other low-grade nodal lymphomas, such as the follicular or small lymphocytic lymphomas, but different than MALT-type lymphoma.

Clinical significance of follicular lymphoma with monocytoid B cells. Non-Hodgkin's Lymphoma Classification Project

Although follicular lymphoma (FL) is very common in the Western world, very little information is available regarding the frequency and significance of monocytoid B cells (MBC) in FL. We recently completed a clinicopathologic study of 1,378 cases of non-Hodgkin's lymphoma. In this study, a research data sheet was designed to conduct research on several types of lymphomas, one part of which was evaluating the presence of intrafollicular clear cells and extrafollicular MBC in 326 cases diagnosed as FL by one of the pathologists (B.N.N.). For each case diagnosed as FL, the presence of intrafollicular clear cells or extrafollicular MBC was scored as pure FL (no intrafollicular clear cells or extrafollicular MBC), FL with intrafollicular clear cells, FL with less than 5% MBC, and FL with greater than 5% MBC. Of 326 cases classified as FL, 252 (77%) had no intrafollicular clear cells or extrafollicular MBC and therefore were called pure FL. In 36 cases (11%), intrafollicular clear cells were seen, but no extrafollicular MBC. There were no clinical differences between such cases and the 252 cases of pure FL. In eight cases of FL (2%), MBC clusters were rare (<5%). In contrast, 30 cases of FL (9%) had a prominent (>5%) proliferation of extrafollicular MBC; these 30 cases had a significantly shorter failure-free survival (P = .001) and overall survival (P = .04) than the 252 cases of pure FL. The shorter survival of these 30 cases appeared to be independent of the international prognostic index (IPI), stage, and treatment. The FFS of this group remained shorter than that of cases with pure FL when the analysis was restricted to patients treated with Adriamycin-containing regimens and either a favorable (0 to 3) IPI score (P = .001) or advanced stage (III/IV) disease (P = .015). In conclusion, FL with a prominent (>5%) MBC component constitutes a substantial proportion (9%) of FL and has distinctive morphology, and these patients have a significantly shorter survival than those with pure FL.