Nodular lymphocyte predominant Hodgkin lymphoma: pathology, clinical course and relation to T-cell/histiocyte rich large B-cell lymphoma.

Nodular lymphocyte predominant Hodgkin lymphoma (NLPHL) is an unusual subtype of Hodgkin lymphoma characterised by a distinct histopathological and clinical presentation. It mostly affects males and presents with localised disease and an indolent clinical course in the majority of cases. However, there are also patients with advanced NLPHL who frequently present with spleen and liver involvement, B-symptoms and a more aggressive clinical course. Different clinical presentations correlate with distinct histopathological characteristics. NLPHL can be divided into typical and variant histopathological growth patterns. The clinical course of most patients with a typical growth pattern is indolent whereas patients with a variant histology more often present with advanced stage disease and relapse occurs more frequently and earlier. Despite these differences, the prognosis after stage-adapted treatment is favourable for both patient groups. Some cases presenting with a variant histology show a histopathological and clinical overlap with T-cell/histiocyte rich large B-cell lymphoma (THRLBCL). Although being considered as aggressive B-cell lymphoma, THRLBCL exhibits many features that are similar to NLPHL, indicating a close relationship with regard to pathogenesis. Both lymphoma entities derive from germinal centre B-cells, show ongoing somatic hypermutation, and resemble each other in terms of gene expression of tumour cells, genomic imbalances and mutation patterns.