Histopathologic Features and Differential Diagnosis in Challenging Cases of Nodular Lymphocyte Predominant B-cell Lymphoma/Nodular Lymphocyte Predominant Hodgkin Lymphoma.

Abstract

Nodular lymphocyte predominant Hodgkin lymphoma was termed "nodular lymphocyte predominant B-cell lymphoma" in the International Consensus Classification (ICC), to emphasize clinical and biological differences from classic Hodgkin lymphoma (CHL). The abbreviation "NLP" represents both terms in the ICC and World Health Organization classifications. Variations in the growth pattern, originally reported as Fan patterns A-F, are designated as either grade 1 or grade 2 in the ICC. NLP is uncommon, and in some cases an accurate diagnosis is challenging. The objectives of this article were to review the histopathologic features of NLP and the differential diagnosis from other key entities including de novo T-cell/histiocyte-rich large B-cell lymphoma (THRLBL) and lymphocyte-rich classic Hodgkin lymphoma (LRCHL). Histologically, NLP Fan pattern E (THRLBL-like) can be indistinguishable from de novo THRLBL. However, focal nodular areas, clustering of tumor cells, presence of few admixed small B-cells or FDC meshworks, and T-cell rosettes favor NLP Fan pattern E and argue against de novo THRLBL. NLP may also be confused with LRCHL. Patients with NLP are younger than those with LRCHL, and LRCHL may show mediastinal involvement. In LRCHL, the nodular pattern often contains eccentrically located small regressed germinal centers and intact small dense FDC meshworks, in contrast to the expanded, and fragmented FDC meshworks in NLP. Neoplastic cells that are positive for CD30 and CD15 but negative for CD20 and CD79a are characteristic of LRCHL. Additionally, Fascin and Gata3 are commonly positive in LRCHL but usually negative in NLP.