Metalophil histiocytes in non‐Hodgkin's lymphomas particularly in malignant proliferations of B‐lymphocytes

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Abstract
The metalophil method for the demonstration of histiocytes was applied to 108 non-Hodgkin lymphomas diagnosed according to the Kiel classification. In 41 lymphomas the presence of histiocytes was assessed with the aid of the non-specific esterase reaction. The same procedures were performed on 12 lymph nodes with follicular hyperplasia and/or sinus histiocytosis. The number of histiocytes was estimated and graded from 0 to 3. A good correlation between the two methods was found. Dendritic histiocytes were typically absent in lymphocytic lymphomas (CLL type). The follicles were clearly delineated by the distribution of dendritic histiocytes in follicular centroblastic/centrocytic lymphomas. In diffuse centrocytic lymphomas a small to moderate number of siender dendritic histiocytes was seen (grades 1–2). In lymphoplasmacytic/lymphoplasmacytoid lymphomas and in diffuse centroblastic/centrocytic malignant lymphoma the majority showed a great number of pleomorphic dendritic histiocytes (grade 3). In high-grade malignant lymphomas (centroblastic, immunoblastic and lymphoblastic categories) either a high to moderate number of pleomorphic dendritic histiocytes was found or they were totally absent. The lack of histiocytes in centroblastic lymphomas was especially noteworthy. It is proposed that dendritic histiocytes proliferate or are attracted in malignant lymphomas by the presence of centrocytes, especially in combination with centroblasts and by the presence of plasmacytoid cells or their precursors. The frequent absence of dendritic histiocytes in high-grade malignant lymphomas may alternatively be explained by the loss of physiological properties in less differentiated cells.