A new model of pathogenesis (lymph node changes are not “benign tumors” that secrete cytokines, but reactive changes due to excessive cytokine release from an as-yet unknown cause) and a new classification system for MCD (based on HHV-8 status) have ensued. CDCN has launched a platform for online discussion among physicians and researchers, developed a global research agenda, and launched a global patient community in partnership with EURODIS and NORD. Current strategic priorities include: 1) establishing a global patient registry, 2) empowering the global patient community to support one another and join the fight against CD, and 3) distributing high-impact research grants.

For HHV-8-negative MCD (idiopathic MCD), the following treatments have been used: corticosteroids, rituximab, monoclonal antibodies against IL-6 such as tocilizumab and siltuximab, and the immunomodulator thalidomide.

Prior to 1996 MCD carried a poor prognosis of about 2 years, due to autoimmune hemolytic anemia and non-Hodgkin's lymphoma which may arise as a result of proliferation of infected cells. The timing of diagnosis, with particular attention to the difficulty of determining the cause of B symptoms without a CT scan and lymph node biopsy, may have a significant impact on the prognosis and risk of death. Left untreated, MCD usually gets worse and becomes increasingly difficult and unresponsive to current treatment regimens.

Siltuximab prevents it from binding to the IL-6 receptor, was approved by the U.S. Food and Drug Administration for the treatment of multicentric Castleman disease on April 23, 2014. Preliminary data suggest that treatment siltuximab may achieve tumour and symptomatic response in 34% of patients with MCD.

Other treatments for multicentric Castleman disease include the following:

- Corticosteroids

- Chemotherapy

- Thalidomide

Due to the high risk of recurrence and ensuing problems, close monitoring of dogs undergoing chemotherapy is important. The same is true for dogs that have entered remission and ceased treatment. Monitoring for disease and remission/recurrence is usually performed by palpation of peripheral lymph nodes. This procedure detects gross changes in peripheral lymph nodes. Some of the blood tests used in diagnosing lymphoma also offer greater objectivity and provide an earlier warning of an animal coming out of remission.

Complete cure is rare with lymphoma and treatment tends to be palliative, but long remission times are possible with chemotherapy. With effective protocols, average first remission times are 6 to 8 months. Second remissions are shorter and harder to accomplish. Average survival is 9 to 12 months. The most common treatment is a combination of cyclophosphamide, vincristine, prednisone, L-asparaginase, and doxorubicin. Other chemotherapy drugs such as chlorambucil, lomustine (CCNU), cytosine arabinoside, and mitoxantrone are sometimes used in the treatment of lymphoma by themselves or in substitution for other drugs. In most cases, appropriate treatment protocols cause few side effects, but white blood cell counts must be monitored.

Allogeneic and autologous stem cell transplantations (as is commonly done in humans) have recently been shown to be a possible treatment option for dogs. Most of the basic research on transplantation biology was generated in dogs. Current cure rates using stem cell therapy in dogs approximates that achieved in humans, 40-50%.

When cost is a factor, prednisone used alone can improve the symptoms dramatically, but it does not significantly affect the survival rate. The average survival times of dogs treated with prednisone and untreated dogs are both one to two months. Using prednisone alone can cause the cancer to become resistant to other chemotherapy agents, so it should only be used if more aggressive treatment is not an option.

Isotretinoin can be used to treat cutaneous lymphoma.

Chemotherapy is the mainstay of treatment for lymphoma in cats. Most of the drugs used in dogs are used in cats, but the most common protocol uses cyclophosphamide, vincristine, and prednisone. Gastrointestinal lymphoma has also commonly been treated with a combination of prednisolone and high dose pulse chlorambucil with success. The white blood cell count must be monitored. Remission and survival times are comparable to dogs. Lower stage lymphoma has a better prognosis. Multicentric lymphoma has a better response to treatment than the gastrointestinal form, but infection with FeLV worsens the prognosis.

About 75% of cats treated with chemotherapy for lymphoma go into remission. Unfortunately, after an initial remission, most cats experience a relapse, after which they have a median survival of 6 months. However, about one-third of cats treated with chemotherapy will survive more than 2 years after diagnosis; a small number of these cats may be cured of their disease. Untreated, most cats with lymphoma die within 4–6 weeks. Most cats tolerate their chemotherapy well, and fewer than 5% have severe side effects. Cats do not lose their fur from chemotherapy, though loss of whiskers is possible. Other side effects include low white blood cell count, vomiting, loss of appetite, diarrhea, or fatigue. These can typically be controlled well, and most cats have a good quality of life during treatment. If a cat relapses after attaining remission, the cat can be treated with different chemotherapy drugs to try for a second remission. The chances of a second remission are much lower than the chances of obtaining a first, and the second remission is often shorter than the first.

Patients with early stage disease (IA or IIA) are effectively treated with radiation therapy or chemotherapy. The choice of treatment depends on the age, sex, bulk and the histological subtype of the disease. Adding localised radiation therapy after the chemotherapy regimen may provide a longer progression-free survival compared with chemotherapy treatment alone. Patients with later disease (III, IVA, or IVB) are treated with combination chemotherapy alone. Patients of any stage with a large mass in the chest are usually treated with combined chemotherapy and radiation therapy.

It should be noted that the common non-Hodgkin's treatment, rituximab (which is a monoclonal antibody against CD20) is not routinely used to treat Hodgkin's lymphoma due to the lack of CD20 surface antigens in most cases. The use of rituximab in Hodgkin's lymphoma, including the lymphocyte predominant subtype has been recently reviewed.

Although increased age is an adverse risk factor for Hodgkin's lymphoma, in general elderly patients without major comorbidities are sufficiently fit to tolerate standard therapy, and have a treatment outcome comparable to that of younger patients. However, the disease is a different entity in older patients and different considerations enter into treatment decisions.

For Hodgkin's lymphomas, radiation oncologists typically use external beam radiation therapy (sometimes shortened to EBRT or XRT). Radiation oncologists deliver external beam radiation therapy to the lymphoma from a machine called linear accelerator which produces high energy X Rays and Electrons. Patients usually describe treatments as painless and similar to getting an X-ray. Treatments last less than 30 minutes each.

For lymphomas, there are a few different ways radiation oncologists target the cancer cells. Involved field radiation is when the radiation oncologists give radiation only to those parts of the patient's body known to have the cancer. Very often, this is combined with chemotherapy. Radiation therapy directed above the diaphragm to the neck, chest or underarms is called mantle field radiation. Radiation to below the diaphragm to the abdomen, spleen or pelvis is called inverted-Y field radiation. Total nodal irradiation is when the therapist gives radiation to all the lymph nodes in the body to destroy cells that may have spread.

Some patients have no symptoms, spontaneous remission, or a relapsing/remitting course, making it difficult to decide whether therapy is needed. In 2002, authors from Sapienza University of Rome stated on the basis of a comprehensive literature review that "clinical observation without treatment is advisable when possible."

Therapeutic options include surgery, radiation therapy, and chemotherapy. Surgery is used to remove single lymph nodes, central nervous system lesions, or localized cutaneous disease. In 2014, Dalia and colleagues wrote that for patients with extensive or systemic Rosai–Dorfman disease, "a standard of care has not been established" concerning radiotherapy and chemotherapy.

Breast implant-associated ALCL is a recently recognized lymphoma and definitive management and therapy is under evaluation. However, it appears that removal of the implant, and resection of the capsule around the implant as well as evaluation by medical and surgical oncologists are cornerstones. Still under evaluation is the extent of capsulectomy: partial versus complete capsulectomy; similarly it is not defined the significance of replacement of the implant in the affected breast, or the removal of contralateral implant. Similarly, the value of radiation therapy and chemotherapy are under evaluation.

Currently, there is a drug, LDK378, undergoing Phase III clinical trials at Vanderbilt University that targets ALK positive small cell lung cancer, and has showed clinical promise in its previous clinical trials. Because approximately 70% of ALCL neoplasms are also ALK positive, there is hope that similar highly selective and potent ALK inhibitors may be used in the future to treat ALK positive cases of ALCL.

The high cure rates and long survival of many patients with Hodgkin's lymphoma has led to a high concern with late adverse effects of treatment, including cardiovascular disease and second malignancies such as acute leukemias, lymphomas, and solid tumors within the radiation therapy field. Most patients with early-stage disease are now treated with abbreviated chemotherapy and involved-field radiation therapy rather than with radiation therapy alone. Clinical research strategies are exploring reduction of the duration of chemotherapy and dose and volume of radiation therapy in an attempt to reduce late morbidity and mortality of treatment while maintaining high cure rates. Hospitals are also treating those who respond quickly to chemotherapy with no radiation.

In childhood cases of Hodgkin's lymphoma, long-term endocrine adverse effects are a major concern, mainly gonadal dysfunction and growth retardation. Gonadal dysfunction seems to be the most severe endocrine long-term effect, especially after treatment with alkylating agents or pelvic radiotherapy.

Surgical lymph node excision may be carried out at the time of diagnosis in certain cases such in children diagnosed at an early stage of progression. One study found sustained complete remission in half of the cases with a watch-and-wait strategy after surgical lymph node excision at the time of diagnosis.

Watchful waiting (watch and wait) was defined as a period of observation of at least 3 months without any treatment.

The most common chemotherapy used for non-Hodgkin lymphoma is R-CHOP.

Many low-grade lymphomas remain indolent for many years. Treatment of the nonsymptomatic patient is often avoided. In these forms of lymphoma, such as follicular lymphoma, watchful waiting is often the initial course of action. This is carried out because the harms and risks of treatment outweigh the benefits. If a low-grade lymphoma is becoming symptomatic, radiotherapy or chemotherapy are the treatments of choice; although they do not cure the lymphoma, they can alleviate the symptoms, particularly painful lymphadenopathy. Patients with these types of lymphoma can live near-normal lifespans, but the disease is incurable. Some centers advocate the use of single agent rituximab in the treatment of follicular lymphoma rather than the wait and watch approach. Watchful waiting is not a good strategy for all patients, as it leads to significant distress and anxiety in some patients. It has been equated with watch and worry.

Hodgkin lymphoma typically is treated with radiotherapy alone, as long as it is localized.

Advanced Hodgkin disease requires systemic chemotherapy, sometimes combined with radiotherapy. Chemotherapy used includes the ABVD regimen, which is commonly used in the United States. Other regimens used in the management of Hodgkin lymphoma include BEACOPP and Stanford V. Considerable controversy exists regarding the use of ABVD or BEACOPP. Briefly, both regimens are effective, but BEACOPP is associated with more toxicity. Encouragingly, a significant number of people who relapse after ABVD can still be salvaged by stem cell transplant.

Nevertheless, the Working Formulation and the NHL category continue to be used by many. To this day, lymphoma statistics are compiled as Hodgkin's versus non-Hodgkin lymphomas by major cancer agencies, including the US National Cancer Institute in its SEER program, the Canadian Cancer Society and the IARC.

The prognosis varies according with the type of ALCL. During treatment, relapses may occur but these typically remain sensitive to chemotherapy.

Those with ALK positivity have better prognosis than ALK negative ALCL. It has been suggested that ALK-negative anaplastic large-cell lymphomas derive from other T-cell lymphomas that are morphologic mimics of ALCL in a final common pathway of disease progression. Whereas ALK-positive ALCLs are molecularly characterized and can be readily diagnosed, specific immunophenotypic or genetic features to define ALK-negative ALCL are missing and their distinction from other T-cell non-Hodgkin lymphomas (T-NHLs) remains controversial, although promising diagnostic tools for their recognition have been developed and might be helpful to drive appropriate therapeutic protocols.

Systemic ALK+ ALCL 5-year survival: 70–80%.

Systemic ALK- ALCL 5-year survival: 15–45%.

Primary Cutaneous ALCL: Prognosis is good if there is not extensive involvement regardless of whether or not ALK is positive with an approximately 90% 5-year survival rate.

Breast implant-associated ALCL has an excellent prognosis when the lymphoma is confined to the fluid or to the capsule surrounding the breast implant. This tumor can be recurrent and grow as a mass around the implant capsule or can extend to regional lymph nodes if not properly treated.

Treatment with chemotherapy has been used with some success, particularly using lomustine, prednisone, doxorubicin, and cyclophosphamide. Because of the rapid progression of this aggressive disease, the prognosis is very poor.

Current treatment typically includes R-CHOP, which consists of the traditional CHOP, to which rituximab has been added. This regimen has increased the rate of complete response for DLBCL patients, particularly in elderly patients.R-CHOP is a combination of one monoclonal antibody (rituximab), three chemotherapy agents (cyclophosphamide, doxorubicin, vincristine), and one steroid (prednisone). These drugs are administered intravenously, and the regimen is most effective when it is administered multiple times over a period of months. People often receive this type of chemotherapy through a PICC line (peripherally inserted central catheter) in their arm near the elbow or a surgically implanted venous access port. The number of cycles of chemotherapy given depends on the stage of the disease — patients with limited disease typically receive three cycles of chemotherapy, while patients with extensive disease may need to undergo six to eight cycles. A recent approach involves obtaining a PET scan after the completion of two cycles of chemotherapy, to assist the treatment team in making further decisions about the future course of treatment.Older people often have more difficulty tolerating therapy than younger people. Lower intensity regimens have been attempted in this age group.

Radiation therapy is often part of the treatment for DLBCL. It is commonly used after the completion of chemotherapy. Radiation therapy alone is not an effective treatment for this disease.

Currently PTCL is treated similarly to B-cell lymphomas. However, in recent years, scientists have developed techniques to better recognize the different types of lymphomas, such as PTCL. It is now understood that PTCL behaves differently from B-cell lymphomas and therapies are being developed that specifically target these types of lymphoma. Currently, however, there are no therapies approved by the US Food and Drug Administration (FDA) specifically for PTCL. Anthracycline-containing chemotherapy regimens are commonly offered as the initial therapy. Some patients may receive a stem cell transplant. Novel approaches to the treatment of PTCL in the relapsed or refractory setting are under investigation.

Pralatrexate is one compound currently under investigations for the treatment of PTCL. For information please consult the US clinical trials database (http://www.clinicaltrials.gov).

In 2016 the Histiocyte Society proposed a classification of histiocytoses into five groups designated by letters: "C," "H," "L," "M," and "R." Group "R" included Rosai–Dorfman disease and "miscellaneous noncutaneous, non-Langerhans cell histiocytoses." Rosai–Dorfman disease itself was classified into "Familial," "Classical (nodal)," "Extranodal," "Neoplasia-associated," and "Immune disease-associated" subtypes.

Treatment with conventional immunochemotherapy is usually indicated; in younger patients, allogeneic bone marrow transplantation may be curative.

The most successful treatment for angiosarcoma is amputation of the affected limb if possible. Chemotherapy may be administered if there is metastatic disease. If there is no evidence of metastasis beyond the lymphedematous limb, adjuvant chemotherapy may be given anyway due to the possibility of micrometastatic disease. Evidence supporting the effectiveness of chemotherapy is, in many cases, unclear due to a wide variety of prognostic factors and small sample size. However, there is some evidence to suggest that drugs such as paclitaxel, doxorubicin, ifosfamide, and gemcitabine exhibit antitumor activity.

Mast cell tumors mainly occur in older adult dogs, but have been known to occur on rare occasions in puppies. The following breeds are commonly affected by mast cell tumors:

- Boxer

- Staffordshire bull terrier

- Bulldog

- Basset hound

- Weimaraner

- Boston terrier

- Great Dane

- Golden retriever

- Labrador retriever

- Beagle

- German shorthaired pointer

- Scottish terrier

- Pug

- Shar pei

- Rhodesian ridgeback

A similar disease is diffuse histiocytic sarcoma, a term used to designate a localized histiocytic sarcoma that has spread throughout the body.

Another disease of histiocytic origin that affects Bernese Mountain Dogs is systemic histiocytosis. This condition generally begins as lesions on the eyelids, nasal mucosa, and skin, especially the scrotum. It progresses to a more generalized disease affecting the lymph nodes, bone marrow and spleen. Other signs and symptoms include weight loss and loss of appetite. It also has a very poor prognosis.

The B-cell lymphomas are types of lymphoma affecting B cells. Lymphomas are "blood cancers" in the lymph nodes. They develop more frequently in older adults and in immunocompromised individuals.

B-cell lymphomas include both Hodgkin's lymphomas and most non-Hodgkin lymphomas. They are typically divided into low and high grade, typically corresponding to indolent (slow-growing) lymphomas and aggressive lymphomas, respectively. As a generalisation, indolent lymphomas respond to treatment and are kept under control (in remission) with long-term survival of many years, but are not cured. Aggressive lymphomas usually require intensive treatments, with some having a good prospect for a permanent cure.

Prognosis and treatment depends on the specific type of lymphoma as well as the stage and grade. Treatment includes radiation and chemotherapy. Early-stage indolent B-cell lymphomas can often be treated with radiation alone, with long-term non-recurrence. Early-stage aggressive disease is treated with chemotherapy and often radiation, with a 70-90% cure rate. Late-stage indolent lymphomas are sometimes left untreated and monitored until they progress. Late-stage aggressive disease is treated with chemotherapy, with cure rates of over 70%.