DLBCL with distinctive clinical issues
Primary mediastinal large B-cell lymphoma
Primary mediastinal large B-cell lymphoma (PMBL), also termed primary mediastinal (thymic) large B-cell lymphoma, is a DLBCL in which neoplastic B-cells infiltrates are commonly located in sclerotic/fibrous tissues of the thymus and mediastinal lymph nodes. The disease represents 6–10% of all DLBCL cases, presents with early stage disease in ~80% of cases, and has an overall survival rate at 5 years of 75–85%. Primary cutaneous diffuse large B-cell lymphoma, leg type
Primary cutaneous diffuse large B-cell lymphoma, leg type (PCDLBCL-LT) is a DLBCL in which diffuse patterns of immunoblastic and/or centroblastic B-cells infiltrate the dermis and/or subcutaneous tissue principally, but not exclusively, of the legs. This diseases 5-year overall survival rate is 50–60%. Primary diffuse large B-cell lymphoma of the central nervous system
Primary diffuse large B-cell lymphoma of the central nervous system (DLBCL-CNS, also termed primary central nervous system lymphoma [PCNSL]) is a DLBCL in which diffuse patterns of neoplastic B-cells with centroblastic, immunoblastic, or poorly differentiated features infiltrate the brain, spinal cord, leptomeninges, or eye. The disease usually presents as a single lesion with a predilection for the supratentorial region of the brain but may involve the eye in 15–25% of cases, the cerebrospinal fluid in 7–42% of cases, and the spinal cord in ~1% of cases. The disease has a 5-year overall survival rate of ~30%.
In the remaining ~30% of other cases, the disease begins as an extranodal lymphoma, most commonly in the stomach, or, less commonly, in other sites such as the testicles, breasts, uterus, ovaries, kidneys, adrenal glands, thyroid gland, or bone. The presenting signs and symptoms in these cases reflect the presence of a rapidly expanding tumor or infiltrate that produces symptoms specific to the organ of involvement such as increased size, pain, and/or dysfunction. Individuals with nodal or extranodal disease also present with: systemic B symptoms such as weight loss, night sweats, fevers, and/or fatigue in ~33% of cases; unexplained elevations in their blood levels of lactic acid dehydrogenase and beta-2 microglobulin in many cases; malignant cells infiltrating their bone marrow in 10–20% of cases; and/or localized Stage I or II disease in up to 50% of cases and disseminated Stage III or IV disease in the remaining cases. Bone marrow involvement may be due to DLBCL, NOS cells or low grade lymphoma cells; only DLBCL, NOS cell infiltrates indicate a worse prognosis. Uncommonly, DLBCL may arise as a transformation of marginal zone lymphoma (MZL) in individuals who have been diagnosed with this indolent cancer 4–5 years (median times) previously. Prognostic indicators based on clinical presentation
The International Prognostic Index and more recently, the Indexs age-adjusted variant use age >60 years, elevated serum lactate dehydrogenase levels, low performance status, and involvement in more than one extranodal site as contributors to a poor prognosis in patients with DLBCL, NOS.