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Morphology of T-cell/histiocyte-rich large B-cell lymphoma (THRLBCL): The nodal architecture is effaced by a diffuse or vaguely nodular polymorphic infiltrate composed of abundant reactive T-cells and small number of neoplastic large B-cells.
Neoplastic large B-cells: They should comprise less than 10% of the cellular population and are scattered singly, without forming aggregates or sheets, in a background of abundant reactive T-cells. They can resemble centroblasts, immunoblasts, Reed-Sternberg cells, LP cells, or pleomorphic cells with irregular folded nuclei.
Reactive T-cells: They make up the bulk of the cellular component and consist of either normal-appearing or slightly activated small lymphocytes with mild nuclear enlargement and nuclear foldings.
Other cells: In addition to the large neoplastic B-cells and abundant reactive T-cells, there are small numbers of histiocytes, eosinophils, and plasma cells. Meshworks of follicular dendritic cells are not seen. Areas of trabecular fibrosis are common.
Any areas resembling nodular lymphocyte-predominant Hodgkin lymphoma (NLPHL) on morphology or immunophenotyping exclude the diagnosis of THRLBCL. Such cases are more appropriately interpreted as diffuse growth of NLPHL.
Neoplastic large B-cells: They should comprise less than 10% of the cellular population and are scattered singly, without forming aggregates or sheets, in a background of abundant reactive T-cells. They can resemble centroblasts, immunoblasts, Reed-Sternberg cells, LP cells, or pleomorphic cells with irregular folded nuclei.
Reactive T-cells: They make up the bulk of the cellular component and consist of either normal-appearing or slightly activated small lymphocytes with mild nuclear enlargement and nuclear foldings.
Other cells: In addition to the large neoplastic B-cells and abundant reactive T-cells, there are small numbers of histiocytes, eosinophils, and plasma cells. Meshworks of follicular dendritic cells are not seen. Areas of trabecular fibrosis are common.
Any areas resembling nodular lymphocyte-predominant Hodgkin lymphoma (NLPHL) on morphology or immunophenotyping exclude the diagnosis of THRLBCL. Such cases are more appropriately interpreted as diffuse growth of NLPHL.