Of all cancers involving the same class of blood cell, 8% of cases are MALT lymphomas.

Of all cancers involving the same class of blood cell (lymphoproliferative disorders), 22% of cases are follicular lymphomas.

Histologic transformation to diffuse large B-cell lymphoma (DLBCL) can occur in up to 12% of cases. After transformation, neoplastic cells carry monoclonal immunoglobulin gene rearrangements. Histological transformation may lead to poor prognosis and therefore repeat biopsy is required at relapse.

One study found a transformation rate of 7.6%, and suggested that prior exposure to chemotherapy and a presentation with splenic involvement were associated with increased risks of transformation.

One study has suggested improved overall survival in response to chemotherapy for African Americans.

Median survival is around 10 years, but the range is wide, from less than one year, to more than 20 years. Some patients may never need treatment. The overall survival rate at five years is 72–77%. Recent advances and addition of Rituximab, improved median survival. Recent reports for the period 1986 and 2012 estimates median survival of over 20 years.

This rare form of leukemia is more common among Asians in comparison to other ethnic groups. It is typically diagnosed in adolescents and young adults, with a slight predominance in males.

The factors of poor prognosis for patients with thyroid lymphoma are advanced stage of the tumor, large size (>10 cm) as well as spreading to mediastinum. The overall survival for primary thyroid lymphoma is 50% to 70%, ranging from 80% in stage IE to less than 36% in stage IIE and IVE in 5 years.

Primary cerebral lymphoma (or "primary central nervous system lymphoma") is a form of NHL. It is very rare in immunocompetent people, with an incidence of 5–30 cases per million person-years. However the incidence in immunocompromised individuals is greatly increased, up to 100 per million person-years.

Primary cerebral lymphoma is strongly associated with Epstein–Barr virus (EBV). The presence of EBV DNA in cerebrospinal fluid is highly suggestive of primary cerebral lymphoma.

Treatment of AIDS patients with antiretroviral drugs reduces the incidence of primary cerebral lymphoma.

The incidence of Hodgkin's disease in the general population is about 10–30 per million person-years. This increases to 170 per million person-years in HIV positive patients.

Treatment of Hodgkin's disease has been improving over the past few decades. Recent trials that have made use of new types of chemotherapy have indicated higher survival rates than have previously been seen. In one recent European trial, the 5-year survival rate for those patients with a favorable prognosis (FFP) was 98%, while that for patients with worse outlooks was at least 85%.

In 1998, an international effort identified seven prognostic factors that accurately predict the success rate of conventional treatment in patients with locally extensive or advanced stage Hodgkin's lymphoma. Freedom from progression (FFP) at 5 years was directly related to the number of factors present in a patient. The 5-year FFP for patients with zero factors is 84%. Each additional factor lowers the 5-year FFP rate by 7%, such that the 5-year FFP for a patient with 5 or more factors is 42%.

The adverse prognostic factors identified in the international study are:

- Age ≥ 45 years

- Stage IV disease

- Hemoglobin < 10.5 g/dl

- Lymphocyte count < 600/µl or < 8%

- Male

- Albumin < 4.0 g/dl

- White blood count ≥ 15,000/µl

Other studies have reported the following to be the most important adverse prognostic factors: mixed-cellularity or lymphocyte-depleted histologies, male sex, large number of involved nodal sites, advanced stage, age of 40 years or more, the presence of B symptoms, high erythrocyte sedimentation rate, and bulky disease (widening of the mediastinum by more than one third, or the presence of a nodal mass measuring more than 10 cm in any dimension.)

More recently, use of positron emission tomography (PET) early after commencing chemotherapy has demonstrated to have powerful prognostic ability. This enables assessment of an individual's response to chemotherapy as the PET activity switches off rapidly in patients who are responding. In this study, after two cycles of ABVD chemotherapy, 83% of patients were free of disease at 3 years if they had a negative PET versus only 28% in those with positive PET scans. This prognostic power exceeds conventional factors discussed above. Several trials are underway to see if PET-based risk adapted response can be used to improve patient outcomes by changing chemotherapy early in patients who are not responding.

Of all cancers involving the same class of blood cell, 8% of cases are mature T cell lymphomas. Of such cases, 2% are precursor T lymphoblastic and 2% are cutaneous T cell lymphomas.

Unlike some other lymphomas, whose incidence increases with age, Hodgkin's lymphoma has a bimodal incidence curve; that is, it occurs most frequently in two separate age groups, the first being young adulthood (age 15–35) and the second being in those over 55 years old although these peaks may vary slightly with nationality. Overall, it is more common in males, except for the nodular sclerosis variant, which is slightly more common in females. The annual incidence of Hodgkin's lymphoma is 2.7 per 100,000 per persons per year, and the disease accounts for slightly less than 1% of all cancers worldwide.

In 2010, globally it resulted in about 18,000 deaths down from 19,000 in 1990.

The incidence of Hodgkin's lymphoma is increased in patients with HIV infection. In contrast to many other lymphomas associated with HIV infection it occurs most commonly in patients with higher CD4 T cell counts.

The 5 year survival has been noted as 89% in at least one study from France of 201 patients with T-LGL leukemia.

Chemotherapy with CHOP, infusional EPOCH, hyperCVAD, and CODOX-M/IVAC is often used. The prognosis is generally poor, for example 6 to 7 months and 14 months.

Peripheral T-cell lymphoma refers to a group of T-cell lymphomas that develop away from the thymus.

Examples include:

- Cutaneous T-cell lymphomas

- Angioimmunoblastic T-cell lymphoma

- Extranodal natural killer/T-cell lymphoma, nasal type

- Enteropathy type T-cell lymphoma

- Subcutaneous panniculitis-like T-cell lymphoma

- Anaplastic large cell lymphoma

- Peripheral T-cell lymphoma-Not-Otherwise-Specified

In ICD-10, cutaneous T-cell lymphomas are classified separately.

The T-cell lymphomas are four types of lymphoma that affect T cells. These account for about one in ten cases of non-Hodgkin lymphoma.

They can be associated with Epstein Barr virus and Human T-cell leukemia virus-1.

A second regimen under evaluation is R-EPOCH (rituximab with etoposide-prednisone-vincristine-doxorubicin-cyclophosphamide), which demonstrated a 5-year progression-free survival (PFS) of 79% in a phase II trial. A phase III trial, CALGB 50303, is now comparing R-EPOCH with R-CHOP in patients with newly diagnosed DLBCL.

One area of active research is on separating patients into groups based on their prognosis and how likely they are to benefit from different drugs. Methods like gene expression profiling and next-generation sequencing may result in more effective and more personalized treatment.

Additionally, some researchers separate out lymphomas that appear to result from other immune system disorders, such as AIDS-related lymphoma.

Classic Hodgkin's lymphoma and nodular lymphocyte predominant Hodgkin's lymphoma are now considered forms of B-cell lymphoma.

Pralatrexate is one compound currently under investigations for the treatment of PTCL.

In the United States, about 500 patients are diagnosed with Richter's transformation each year.

One classification system for lymphomas divides the diseases according to the size of the white blood cells that has turned cancerous. The large-cell lymphomas have large cells. A large cell, in this context, has a diameter of 17 to 20 µm. Other groups of lymphomas in this system are the small-cell lymphomas and mixed-cell lymphomas.

Castleman disease (CD) is a lymphoproliferative disorder of unknown cause. CD is associated with an increased risk of B-cell lymphoma.

Human herpesvirus 8 (HHV-8), also known as Kaposi sarcoma-associated herpesvirus (KSHV) has been found in some cases of multicentric Castleman disease (MCD). The HHV8 can give rise to an increased number of plasmablast cells within the mantle zone of B-cell follicles. These plasmablasts express IgM-immunoglobulin light chains, most often of lambda subtype. These plasmablasts can give rise to a spectrum of abnormalities including progression to microlymphoma (microscopic clusters of plasmablast cells) or clinical lymphoma.

This type of lymphoma is predominantly seen in acquired immunodeficiencies, including acquired immunodeficiency syndrome (AIDS) but it can also occur in immunosuppression such as with organ transplantation or the elderly. The plasmablasts do not show rearranged immunoglobulin genes, and typically lack EBV infection.

The disease predominantly affects lymph nodes and the spleen, a pattern dissimilar to plasmablastic lymphoma of the oral cavity of AIDS which is not associated with HHV-8 infection. Despite traditional chemotherapy with CHOP (cyclophosphamide, doxorubicin, prednisone, vincristine), and the possible addition of antiviral therapy and inhibition of specific cellular targets including the use of rituximab, the prognosis in this lymphoma has been poor.

This lymphoma subtype has sometimes been confused with plasmablastic lymphoma in the literature, although that is a dissimilar specific entity. Similarly, this subtype is considered distinct from other lymphomas which have a plasmablastic immunophenotype such as primary effusion lymphoma, ALK+ large B-cell lymphoma, and extracavitary HHV–8-positive lymphoma.

HHV8 is also associated with Kaposi's sarcoma and with another subtype of lymphoma, primary effusion lymphoma, previously called body cavity-based lymphoma.

The prognosis is generally poor. The "RS score" (Richter syndrome score), which is an estimate of the patient's prognosis, is based on the patient's performance status, LDH, platelet count, the size of the lymphoma tumors, and the number of prior therapies already received. Overall, the median survival is between five and eight months. Untreated, RS is invariably fatal.

The Hodgkin's lymphoma variant of Richter's carries a better prognosis than the predominant diffuse large B-cell lymphoma type, but a worse prognosis than a "de novo" case of Hodgkin's.

Multiagent chemotherapy is recommended, but the preferred regimen is controversial, as is consolidative radiotherapy.

"MALT lymphoma" is exquisitely immunotherapy sensitive. Chemotherapy is reserved for those uncommon patients with disseminated disease at presentation or lack of response to local treatment. Rituximab, the anti-CD20 chimeric antibody, is a key component of therapy. Responses vary from 55% to 77% with monotherapy and 100% in combination with chemotherapy. Oral alkylating agents such as cyclophosphamide or chlorambucil have been administered for a median duration of 12 months with high rates of disease control (CR up to 75%) but appear not to be active in t(11;18) disease. The purine nucleoside analogs fludarabine and cladribine also demonstrate activity, the latter conferring a CR rate of 84% (100% in those with gastric primaries) in a small study. A pivotal study of rituximab plus chlorambucil compared with chlorambucil alone (IELSG-19 study, n = 227) demonstrated a significantly higher CR rate (78% vs. 65%; p = 0.017) and 5-year EFS (68% vs. 50%; p = 0.024) over chlorambucil alone. However, 5-year OS was not improved (88% in both arms). First-line treatment of choice is generally rituximab in combination with single alkylating agents or fludarabine, or a combination of all three drugs. The final results of this study, including the later addition of a rituximab-alone arm, are pending.

Two other genetic alterations are known:

- t(1;14)(p22;q32), which deregulates BCL10, at the locus 1p22.

- t(14;18)(q32;q21), which deregulates MALT1, at the locus 18q21.

These seem to turn on the same pathway as API2-MLT (i.e., that of NF-κB). They both act upon IGH, which is at the locus 14q32.