Diffuse Mixed Lymphoma 

Diffuse mixed lymphomas are classified as diffuse large B-cell lymphomas. Clinically, patients with this type of lymphoma usually present with advanced and, often, extranodal disease.

A number of risk factors have been associated with non-Hodgkin lymphomas (NHLs) in general. These include Epstein-Barr virus (EBV) infection, human immunodeficiency virus (HIV) infection, pesticides, hair dyes, primary and transplant-related immunodeficiency, and rheumatoid arthritis (RA) and other autoimmune disorders. Occupational factors have a weak or an inconsistent risk.

Diffuse mixed lymphomas comprise approximately 30% of all non-Hodgkin lymphomas (NHLs), and affect females more often than males as well as older individuals. Most patients with diffuse mixed lymphomas are diagnosed during the seventh or eighth decade of life, with a median age of 63 years.

Historical classification

In 1956, Rappaport initially described a subset of non-Hodgkin lymphoma (NHL) that was characterized by a mixed population of diffusely infiltrating malignant histiocytes and lymphocytes; he referred to them as mixed histiocytic-lymphocytic malignant lymphomas. These malignant histiocytes were later identified as lymphocytes; thus, the term “malignant lymphoma, mixed small and large cell,” was adopted. Histologically, these lymphomas contain an equal number of small and large cells (30-70%) (see the image below).

In the Working Formulation classification system proposed by a National Cancer Institute working group in 1982, these lymphomas were classified as an intermediate-grade non-Hodgkin lymphoma (NHL), representing 3-11% of all non-Hodgkin lymphomas.

With the development of immunophenotypic and molecular diagnostics, the Revised European-American Lymphoma (REAL) classification was subsequently proposed and then modified by the World Health Organization (WHO) in 2001. Diffuse mixed lymphoma is now classified as diffuse large B-cell lymphoma. Clinically, patients with this type of lymphoma usually present with advanced and, often, extranodal disease.

See Staging. Also see B-Cell Lymphoma for more information.

Similar to all other intermediate-grade lymphomas, the mixed small and large cell non-Hodgkin lymphomas (NHLs) most often manifest as primary nodal disease, although involvement of the spleen and other organs is common.

Patients with diffuse mixed lymphomas usually present with lymphadenopathy, most commonly affecting either the cervical or inguinal region. Other common complaints from the history findings may include the following:

• B symptoms (eg, fever, night sweats, >10% weight loss)
• Anorexia
• Pedal edema (caused by pelvic lymphadenopathy)
• Fatigue
• Chest discomfort or shortness of breath (caused by mediastinal lymphadenopathy)

The following are common findings on physical examination:

• Lymphadenopathy (ie, cervical, axillary, inguinal)
• Splenomegaly
• Low-grade fever
• Pedal edema, resulting from extensive pelvic lymphadenopathy

Diffuse mixed lymphomas are staged according to the commonly used Ann Arbor staging system, as follows:

• Stage I – Involvement of a single lymph node region or lymphoid structure (ie, spleen, thymus, Waldeyer ring) or involvement of a single extralymphatic site (IE)
• Stage II – Involvement of 2 or more lymph node regions on the same side of the diaphragm; localized contiguous involvement of only 1 extranodal site and 1 lymph node region on the same side of the diaphragm
• Stage III – Involvement of lymph node regions on both sides of the diaphragm
• Stage IV – Diffuse or disseminated involvement of 1 or more extranodal organs or tissues, with or without associated lymph node involvement

The following conditions are considered in the differential diagnosis of diffuse mixed lymphomas:

• Lymphoma, Mantle Cell
• Lymphoma, Non-Hodgkin
• Sarcoidosis
• Tuberculosis

In patients with suspected diffuse mixed lymphoma, obtain a complete blood cell (CBC) count to evaluate involvement of the bone marrow, which may result in anemia, thrombocytopenia, and/or leukopenia.

Obtain serum electrolyte levels, as electrolyte abnormalities may occur from renal involvement with lymphoma. Abnormal renal function may require a chemotherapy dose adjustment.

Elevated levels of lactate dehydrogenase (LDH) and uric acid correspond with the tumor burden. The LDH value is part of the International Prognostic Index (IPI) and a useful indicator the extent of disease and of the response to treatment; it can be used as an early nonspecific indicator of disease relapse.^[1] An elevated uric acid level also signifies an increased likelihood of tumor lysis syndrome with chemotherapy.

Hepatitis B testing is performed in patients undergoing combination chemoimmunotherapy with rituximab (risk of activation).

Flow cytometry to determine the expression of different immunophenotypes helps in determining a clonal cell population and in differentiating between B- or T-cell origins.

Cytogenetic or fluorescent in situ hybridization (FISH) studies may reveal common chromosomal translocations, such as the following:

• t(3q27) (bcl-6) – Occurs in 35% of patients
• t(14;18)(q32;q21) (bcl-2) – Occurs in 15-20% of patients
• t(8;14)(q24;q32) – Occurs in less than 5% of patients

Gene expression profiling may be able to distinguish 2 separate subtypes of diffuse mixed lymphomas with different prognoses (normal germinal center B-cell pattern vs activated B-cell–like), and results from gene rearrangement studies can be used to establish clonality.^{[2, 3]}

Computed tomography (CT) scans of the neck, chest, abdomen, and pelvis are used to help identify the degree of lymphadenopathy, the presence or absence of extranodal disease, and/or the presence of visceral involvement. CT scans are also part of the complete staging workup for diffuse mixed lymphoma. In addition, baseline CT scan findings aid in disease follow-up care after chemotherapy to assess the degree of response to therapy, as well as aid in planning consolidating radiation therapy, if used. See the images below.

Findings from positron emission tomography (PET) scanning for glucose uptake can indicate areas of increased metabolic activity and can be useful to help determine whether residual masses represent scars or persistent lymphoma, in addition to their frequent use in initial disease staging. PET scan findings are being investigated as prognostic indicators during treatment (after 2-4 cycles), but the clinical utility of this is still unclear.

Gallium scans provide an estimate of the extent of disease and are sometimes used as a means of assessing sites of relapse, as shown in the image below, whereas multigated acquisition (MUGA) scans are used to evaluate the patient's ejection fraction before chemotherapy, because anthracyclines used in the treatment of diffuse mixed lymphomas have a potential cardiotoxic effect.

Bone marrow aspiration and biopsy is performed as part of the staging process to help rule out involvement with lymphoma. However, lymph node biopsy is required to establish a definitive diagnosis of non-Hodgkin lymphoma (NHL); this should be an excisional biopsy rather than a needle biopsy, because nodal architecture is often difficult to assess when small amounts of tissue are used. The diagnosis of diffuse mixed lymphoma is usually confirmed after positive findings are obtained from a lymph node biopsy specimen. Pathology findings in patients with possible diffuse, mixed cell non-Hodgkin lymphoma should be reviewed by an expert hematopathologist, because lymphomas can be difficult to classify.

Diffuse mixed lymphomas are more or less composed of equal numbers of small and large cells. The small cells are usually slightly larger than normal lymphocytes, and they have a cleaved or indented nucleus and coarse chromatin. The large cells can be cleaved or noncleaved. The cytoplasm of these cells is pale, and the cells have an irregular, central, indented nucleus with inconspicuous nucleoli. A subset of the large cells has rounded nuclei with one or more nucleoli; these are the noncleaved large cells and are somewhat larger compared with the cleaved cells. See the following image.

Combination chemoimmunotherapy is the standard of care for all stages of diffuse, mixed-cell non-Hodgkin lymphoma (NHL), with abbreviated chemotherapy and local irradiation as an option for early-stage disease. That is, chemotherapy remains the mainstay of treatment in patients with diffuse mixed lymphoma. Many different regimens are used, but, to date, no single regimen has been shown to be superior to the standard cyclophosphamide, doxorubicin, vincristine, and prednisone plus rituximab (CHOP/R) regimen.

Most patients are treated in an outpatient setting. However, hospitalization may be necessary for patients with the following possible disease- or therapy-associated complications, such as the following:

• Tumor lysis syndrome: Patients with a high tumor burden may need to be admitted to the hospital for prevention of this severe and potentially life-threatening condition to receive prophylaxis with allopurinol and alkaline hydration
• Neutropenic fever: Patients are usually expected to be neutropenic approximately 10-14 days after a dose of chemotherapy, and individuals are most susceptible to infections at this point. If febrile, they should be admitted to the hospital and treated with intravenous antibiotics.
• Anemia and thrombocytopenia: Transfusions (red blood cells or platelets) should be administered as clinically indicated for anemia and thrombocytopenia.

Diet and activity

A regular diet is recommended for patients with diffuse mixed lymphoma; however, a neutropenic diet is suggested during periods of neutropenia. No activity limitations are recommended; however, the lymphoma, its treatment, or both may result in substantial fatigue.

Consultations

Because multiple chemotherapy cycles are usually administered, consult a surgeon regarding implantation of a venous access device, which is helpful for chemotherapy infusions and for the repeated blood samples required to monitor treatment toxicity. Surgical consultation may also be required to obtain a lymph node or tissue biopsy sample. In addition, consult a radiation oncologist in early-stage diffuse mixed lymphoma.

Transfer

Patients whose conditions relapse after multiple treatment regimens or who have poor performance status are thus not candidates for further chemotherapy and should be considered for palliative management and hospice care. The following services can be sought in appropriate clinical situations:

• Pain management service
• Nursing home
• Terminal care facility (hospice)
• Home care with specialized nursing support for pain management
• Rehabilitative centers

For early stage diffuse mixed lymphoma disease (stage I or nonbulky stage II), combined-modality therapy, usually incorporating a regimen of 3 cycles of cyclophosphamide, doxorubicin, vincristine, and prednisone plus rituximab (CHOP/R) with involved-field radiation therapy (IFRT), has been used.^[4] The addition of rituximab, an anti-CD20 antibody, has proved very beneficial in lymphoma treatment. Studies have suggested that 4 cycles of CHOP may be at least as good as CHOP plus radiotherapy (RT) in patients older than 60 years.

For advanced-stage disease (II bulky, III, and IV), systemic chemotherapy with the CHOP/R regimen is the standard of care. This combination has been shown to be superior to CHOP alone.^{[5, 6, 7]}

CHOP/R regimens

The CHOP/R regimen is administered intravenously (IV) every 21 days and consists of 750 mg/m² of cyclophosphamide (Cytoxan) on day 1, 50 mg/m² of doxorubicin (Adriamycin) on day 1, 2 mg of vincristine on day 1, 375 mg/m² of rituximab on day 1, and oral (PO) 100 mg of prednisone on days 1-5. This combination is moderately emetogenic and should be accompanied by aggressive antiemetics.

Dose-dense CHOP/R is a more intensive regimen given every 14 days instead of 21, with the addition of growth factors (colony-stimulating factor [G-CSF] or granulocyte monocyte colony stimulating factor [GM-CSF]). This regimen is being evaluated relative to standard CHOP/R in an ongoing trial.

The following regimens have also been used for the treatment of intermediate-grade non-Hodgkin lymphoma and may be used as salvage therapy in cases of relapse.

The DHAP chemotherapy regimen consists of the following:

• Dexamethasone (40 mg PO/IV on days 1-4)
• Cisplatin (100 mg/m²/d via continuous infusion on day 1)
• Cytarabine (2000 mg/m² IV q12h for 2 doses on day 2)

The ESHAP chemotherapy regimen consists of the following:

• Etoposide (40 mg/m² IV on days 1-4)
• Methylprednisolone (500 mg IV on days 1-4)
• Cisplatin (25 mg/m² via continuous infusion on days 1-4)
• Cytarabine (2000 mg/m² IV on day 5)
• ICE (ifosfamide, carboplatin, etoposide)

Other regimens are now only considered for patients whose condition relapses and who are not candidates for high-dose chemotherapy (HDC) and autologous stem cell transplantation (ASCT) for diffuse mixed lymphoma.^{[8, 9]}

• ICE – Ifosfamide, carboplatin, etoposide
• ProMACE-MOPP – Prednisone, methotrexate, leucovorin calcium, doxorubicin, cyclophosphamide, etoposide, mechlorethamine, vincristine, procarbazine, prednisone
• MACOP-B – Methotrexate, doxorubicin, cyclophosphamide, vincristine, bleomycin, prednisone, leucovorin calcium, trimethoprim/sulfamethoxazole DS, ketoconazole
• ProMACE-CytaBOM – Prednisone, doxorubicin, cyclophosphamide, etoposide, cytarabine, bleomycin, vincristine, methotrexate, leucovorin calcium, concomitant trimethoprim/sulfamethoxazole DS

HDC and ASCT

Patients whose condition relapses and who have chemoresponsive disease, as evaluated after salvage therapy, should be considered for HDC followed by stem cell rescue. The Parma trial unequivocally established the superiority of HDC and ASCT over conventional salvage treatments.^[10] In this trial, patients younger than 60 years with non-Hodgkin lymphoma ranging from intermediate grade to high grade who were in their first or second disease relapse were given 2 doses of the DHAP chemotherapy regimen (cisplatin, cytarabine, dexamethasone).^[10]

Those patients with responsive disease were then randomly selected to receive either 4 courses of conventional chemotherapy or HDC plus ASCT.^[10] At 8-year follow-up, the reported overall survival (OS) rate was 47% in the HDC arm versus 27% in the DHAP arm, and the event-free survival rate was 36% in the HDC arm compared with 11% in the DHAP arm.^[10] How these results can be applied in the current era, in which the initial treatment almost always incorporates rituximab, is unclear.

The Groupe d' Etudes des Lymphomes de l' Adults studied the role of HDC and ASCT in early or late intensification and found that the overall survival rate in the late intensification arm was 44% versus 22% in the early intensification group. This finding suggested that HDC plus ASCT should not be considered in patients with untested relapse.

Current recommendations are to consider HDC and ASCT for patients in their first relapse, after chemoresponsiveness is established with a second-line salvage therapy. The role of HDC plus ASCT in first complete response for patients whose disease has a slow initial response to first-line chemotherapy, those with poor initial prognostic factors, or as upfront therapy has not been clearly defined and remains controversial.

Investigative regimens

A German trial explored the safety and feasibility of dose-escalated cyclophosphamide, doxorubicin, vincristine, and prednisone (CHOP)–etoposide with 3 ASCTs as aggressive up-front therapy in young patients with high lactate dehydrogenase (LDH) levels.^[11] The investigators found the therapy safe and feasible, but its role is unclear. Rituximab was not used, and whether these intensive regimens are better than less intense chemotherapy plus rituximab is currently under investigation.

Antisense therapy (Bcl-2 antisense therapy) has entered clinical trials with promising results; however, its role outside a clinical trial is not yet established.

The addition of bortezomib, a protease inhibitor approved for treatment of myeloma, to CHOP/R (rituximab) is also being investigated in phase I and II trials.^[12]

Multicenter trials of radioimmunotherapy with ibritumomab tiuxetan (yttrium-90 [⁹⁰ Y] Zevalin) and iodine-131 [¹³¹ I] tositumomab (Bexxar), CD20-targeting radiolabeled antibodies approved for use in follicular lymphomas, are also ongoing.

Antiemetics are used as supportive medication for the prevention of chemotherapy-induced nausea and vomiting, including the following:

• The 5-hydroxytriptamine 3 (5-HT3) antagonists such as granisetron (1 mg orally [PO] q12h) or ondansetron (8 mg PO q8h) for severe chemotherapy-induced nausea and vomiting
• Lorazepam (1 mg PO/SL q4-6h)
• Metoclopramide (0.5-2 mg/kg PO q3-4h)
• Prochlorperazine (10 mg PO q4-6h)

Palonosetron (Aloxi) is a selective 5-HT3 receptor antagonist with a long half-life (40 h). The adult dose is intravenous (IV) 0.25 mg once (30 min before chemotherapy). Administer IV over 30 seconds, and do not repeat the dose within 7 days. Palonosetron may cause headache, constipation, diarrhea, or dizziness.

For patients with anemia, consider erythropoietin or epoetin alfa (Procrit) at 40,000-60,000 U subcutaneously [SC] once per week, or darbepoetin alfa 300 mcg SC weekly.

Growth factors stimulate blood cell production. Endogenous erythropoietin stimulates red blood cell hematopoiesis. Recombinant human erythropoietin (epoetin alfa) stimulates erythropoiesis in anemic conditions. Colony-stimulating factors act on hematopoietic cells to stimulate hematopoietic progenitor cells proliferation and differentiation. Interleukins stimulate stem cell proliferation.

Chemotherapy-associated complications may include the following:

• Cardiomyopathy (related to anthracycline)
• Infections (during neutropenia, postchemotherapy)
• Gonadal dysfunction (sterility related to chemotherapy)
• Secondary leukemias (exposure to alkylating agents)
• Alopecia
• Neuropathy
• Related to bone marrow transplantation

Patients with induction-failure non-Hodgkin lymphoma (NHL) (ie, those with chemosensitive disease who do not achieve complete response with primary therapy) or recurrent NHL should be carefully selected for bone marrow transplantation. Only patients with chemosensitive disease should be considered for high-dose chemotherapy (HDC) and autologous stem cell transplantation (ASCT).

Special concerns

A medicolegal pitfall includes failure to inform patients with diffuse mixed lymphomas about the long-term sequelae of chemotherapeutic agents, which include the following:

• Infertility
• Secondary leukemias
• Myelodysplastic syndrome
• Possible anaphylactic reactions
• Serious and potentially fatal infections

Other potential pitfalls include the following:

• Failure to clearly explain transfusions (both red blood cells and platelets) and associated complications
• Failure to discuss the possibility of: (1) long-term complications of higher doses of chemoradiotherapy and (2) mortality rates as high as 3-5% from the conditioning regimen in those who require HDC and ASCT

Patients with diffuse large B-cell lymphomas (diffuse mixed lymphomas) should be educated about the following:

• Febrile neutropenia
• Postchemotherapy thrombocytopenia and the tendency to bleed with minimal trauma
• Chemotherapy-associated alopecia
• Avoidance of pregnancy in reproductive-aged women
• Chemotherapy-induced nausea and vomiting
• Chemotherapy-associated menstrual dysregulation (females) and the possibility of sexual dysfunction
• Fatigue
• Sperm banking and risk of sterility for males

Administer growth factor support (ie, GM-CSF, G-CSF) to patients with a previous episode of febrile neutropenia during subsequent cycles. Patients who administer growth factors to themselves should be carefully advised on sterile techniques, and patients with fevers during periods of neutropenia should immediately seek the attention of the treating physician.

Red blood cell transfusions or erythropoietin or darbepoetin alfa (Aranesp) injections may be required for patients with persistently low hemoglobin values due to disease or chemotherapy.

For patient education information, see the Blood and Lymphatic System Center, as well as Lymphoma.

Based on the International Prognostic Index (IPI), patients with diffuse mixed lymphomas can be grouped into the prognostic categories of low risk (category 0 or 1), low-intermediate risk (category 2), high-intermediate risk (category 3), and high risk (category 4 or 5).^[1] The 5 factors rated in the IPI are age, lactate dehydrogenase (LDH) level, stage, performance status, and number of extranodal sites.^[13]

The IPI uses 5 pretreatment characteristics to identify the various risk groups, which are as follows:

• Age (< 60 y vs >60 y)
• Number of extranodal sites of involvement (< 1 vs >1)
• Tumor stage I or II (localized) versus III or IV (advanced)
• Patient performance status (0 or 1 vs >2)
• Serum lactate dehydrogenase (LDH) level (normal vs abnormal)

Based on the 5 IPI characteristics, patients are classified into 4 categories:

• Category 4 or 5: High risk, 4 or 5 adverse factors
• Category 3: High-intermediate risk, 3 adverse factors
• Category 2: Low-intermediate risk, 2 adverse factors
• Category 0 or 1: Low risk, 0 or 1 adverse factor

For intermediate and aggressive lymphomas, the complete remission (CR) rate for low-risk patients is 87%, and the 5-year overall survival (OS) rate is 73%. The CR rate for high-risk patients is 44%, and the 5-year OS rate is 26%

The 5-year relapse-free survival rate for low-risk patients is 70%, and the 5-year OS rate is 73%. For the high-risk group, the 5-year relapse-free survival rate is 40% and the 5-year OS rate is 26%.