Chapter 105. Malignancies of Lymphoid Cells (Part 2) Non-Hodgkin's lymphomas were separated from Hodgkin's disease by recognition of the Sternberg-Reed cells early in the twentieth century. The histologic classification for non-Hodgkin's lymphomas has been one of the most contentious issues in oncology. Imperfect morphologic systems were supplanted by imperfect immunologic systems, and poor reproducibility of diagnosis has hampered progress. In 1999, the World Health Organization (WHO) classification of lymphoid malignancies was devised through a process of consensus development among international leaders in hematopathology and clinical oncology. The WHO classification takes into account morphologic, clinical, immunologic, and genetic information and attempts to divide non-Hodgkin's lymphomas and other lymphoid malignancies into clinical/pathologic entities that have clinical and therapeutic relevance. This system is presented in Table 105-3. This system is clinically relevant and has a higher degree of diagnostic accuracy than those used previously. The possibilities for subdividing lymphoid malignancies are extensive. However, Table 105-3 presents in bold those malignancies that occur in at least 1% of patients. Specific lymphoma subtypes will be dealt with in more detail below. Lymphomas associated with HIV infection are discussed in Chap. 182. Table 105-3 WHO Classification of Lymphoid Malignancies B Cell T Cell Hodgkin's Disease Precursor B cell neoplasm Precursor T cell neoplasm Nodular lymphocyte- predominant Hodgkin's disease Precursor B lymphoblastic Precursor T lymphoblastic leukemia/lymphoma (precursor B cell acute lymphoblastic leukemia) lymphoma/leukemia (precursor T cell acute lymphoblastic leukemia) Mature (peripheral) B cell neoplasms Mature (peripheral) T cell neoplasms Classical Hodgkin's disease B cell chronic lymphocytic leukemia/small lymphocytic lymphoma T cell prolymphocytic leukemia Nodular sclerosis Hodgkin's disease B cell prolymphocytic leukemia T cell granul ar lymphocytic leukemia Lymphocyte- rich classic Hodgkin's disease Lymphoplasmacytic lymphoma Aggressive NK cell leukemia Mixed- cellularity Hodgkin's disease Splenic marginal Adult T cell Lymphocyte- zone B cell lymphoma (± villous lymphocytes) lymphoma/leukemia (HTLV- I+) depletion Hodgkin's disease Hairy cell leukemia Extranodal NK/T cell lymphoma, nasal type Plasma cell myeloma/plasmacytoma Enteropathy- type T cell lymphoma Extranodal marginal zone B cell lymphoma of MALT type Hepatosplenic γd T cell lymphoma Mantle cell lymphoma Subcutaneous panniculitis- like T cell lymphoma Follicular lymphoma Mycosis fungoides/Sézary syndrome Nodal marginal zone Anaplastic l arge cell B cell lymphoma (± monocytoid B cells) lymphoma, primary cutaneous type Diffuse large B cell lymphoma Peripheral T cell lymphoma, not otherwise specified (NOS) Burkitt's lymphoma/Burkitt cell leukemia Angioimmunoblastic T cell lymphoma Anaplastic large cell ly mphoma, primary systemic type Note: HTLV, human T cell lymphotropic virus; MALT, mucosa- associated lymphoid tissue; NK, natural killer; WHO, World Health Organization. Malignancies in bold occur in at least 1% of patients. Source: Adapted from Harris et al. . Chapter 105. Malignancies of Lymphoid Cells (Part 2) Non-Hodgkin's lymphomas were separated from Hodgkin's disease by recognition of the Sternberg-Reed cells early. higher degree of diagnostic accuracy than those used previously. The possibilities for subdividing lymphoid malignancies are extensive. However, Table 105- 3 presents in bold those malignancies. progress. In 1999, the World Health Organization (WHO) classification of lymphoid malignancies was devised through a process of consensus development among international leaders in hematopathology