In addition, disease that initially involves the testes, breast, or uterus has a relatively high rate of spreading to the central nervous system while disease initially involving the kidneys, adrenal glands, ovaries, or bone marrow has a high rate of spreading to other organs, including the central nervous system. All of these cases as well as cases initially involving the central nervous system have relatively poor to very poor prognoses. Cases initially involving the stomach, thyroid, or a single bone site have relatively good prognoses. Pathophysiology
Most cases of DLBCL, NOS appear to result at least in part from the step-wise development of gene changes such as mutations, altered expressions, amplifications (i.e. increases in the number of copies of specific genes), and tranlocations from normal sites to other chromosomal sites. These changes often result in gains or loses in the production or function of the product of these genes and thereby the activity of cell signaling pathways that regulate the maturation, proliferation, survival, spread, evasion of the immune system, and other malignant behaviors of the cells in which they occur. While scores of genes have been reported to be altered in DLBCL, NOS many of these may not contribute to DLBCL, NOS. Changes in the following genes occur frequently in, and are suspected of contributing to, this diseases development and/or progression. BCL2: This gene is a protooncogene, i.e. a normal gene that can become cancer-causing when mutated or overexpressed. Its product, Bcl-2 protein, regulates cellular apoptosis (i.e.
These lymphomas, termed high-grade B-cell lymphoma with MYC, BL2, and/or BL6 rearrangements or, more simply, DH/THL, are regarded as borderline DLBCL,NOS. They represent 6–14% of all DLBCL, NOS and have had long-term survival rates of only 20–25%. Another variant B-cell lymphoma that is also considered to be a borderline DLBCL, NOS is termed high-grade B-cell lymphoma, not otherwise specified (HGBCL, NOS). These two aggressive borderline B-cell lymphomas were previously grouped together as "B-cell lymphoma, unclassifiable with features intermediate between DLBCL and Burkitt lymphoma" (i.e. BCLU) but were separated into DH/THL and HGBC, NOS by the World Health Organization, 2016. The neoplastic cells in a related variant, double expresser lymphoma (i.e. DEL), express the products of MYC and BCL2 genes, i.e. c-Myc and bcl-2 proteins, respectively, but do not have translocations in either of their genes. DEL, which represents about one-third of all DLBCL, NOS cases, has a poorer prognosis than standard DLBCL, NOS but not as poor as DH/THL cases. Cases in which the neoplastic cells have alterations in the MYC gene or its expression without changes in BLC2 or BLC6 also have a poor prognosis, particularly in cases where the MYC gene translocates (i.e. rearranges) with one of the immunoglobulin gene loci. DLBCL that begin in the testicles are a variant of DLBCL, NOS that some authors suggest should be classified as a distinct DLBCL subtype. This variant, termed Primary testicular diffuse large B-cell lymphoma (PT-DLBCL), is a DLBCL, NOS that in >75% of cases involves activated B-cells, i.e. ABC.