ABSTRACT
Diffuse large B-cell lymphoma (DLBCL) is the most common type of lymphoma, with an annual US incidence of >25,000 cases. Patients with DLBCL have highly variable course, response to treatment, and prognosis, which depend on many clinical, morphological, phenotypic, and genetic parameters. Nodal and extranodal DLBCLs differ in clinical presentation, behavior, and prognosis. DLBCL is composed of sheets of intermediate to large cells displaying centroblastic or immunoblastic cytomorphology. DLBCL with immunoblastic morphology is characterized by large nuclei with a fine chromatin and a single, centrally located prominent macronucleolus with variable amounts of eosinophilic to amphophilic cytoplasm. DLBCL with anaplastic features shows marked pleomorphism of tumor cells that may resemble Reed–Sternberg cells or carcinoma cells. Occasional cases of DLBCL form cohesive sheets of large cells with an amorphous myxoid background resembling metastatic carcinoma. The biological consequences of BCL6 expression in DLBCL might vary according to the presence or absence and the nature of the underlying alteration of the BCL6 gene.
