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Non-Hodgkin lymphoma

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Prolymphocytic leukemias (PLLs)

Prolymphocytic leukemias (PLLs) are rare lymphoid leukemias, which account for only about 2% of all mature lymphoid leukemias. PLLs present like leukemia and, like lymphomas, they start in the lymphocytes, but do not form solid tumours. PLLs are also considered lymphoproliferative disorders, which mean that lymphocytes are produced in large amounts. PLLs were thought to be a rare variation of chronic lymphocytic leukemia (CLL), but are now considered a distinct disease.

  • With CLL, there are too many mature white blood cells (lymphocytes).
  • With PLL, the abnormal lymphocytes are large, immature cells called prolymphocytes, which are not normally found in the blood. A diagnosis of PLL is made when more than half (at least 55%) of the cells in the blood are prolymphocytes.
  • PLL tends to be more aggressive than CLL and does not respond as well to treatment.
  • Sometimes a CLL will change (transform) and take on the appearance of PLL.

PLL often occurs in older people, usually around the age of 65–70. It is slightly more common in men than in women. A person with PLL will usually have an enlarged spleen (splenomegaly) and a very high white blood cell count. Unlike other non-Hodgkin lymphomas (NHLs), the lymph nodes are not usually enlarged.

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Types of PLL

PLL is divided into 2 types based on the type of lymphocyte that the PLL starts in:

  • B-cell prolymphocytic leukemia (B-PLL)
    • About 80% of PLLs are this type.
    • B-PLL usually has a better prognosis than T-PLL.
  • T-cell prolymphocytic leukemia (T-PLL)
    • With T-PLL, leukemia cells can be found in the skin and the liver may be enlarged (hepatomegaly). Lymph nodes are not usually enlarged. Enlarged lymph nodes occur more frequently in T-PLL than in B-PLL.
    • T-PLL is generally more aggressive and doesn’t respond as well to chemotherapy as B-PLL.

Both B-PLL and T-PLL behave fairly aggressively.

Although these 2 types of PLL share some of the same characteristics, the World Health Organization (WHO) classifies them as different types of lymphoid leukemias.

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PLLs are difficult to treat. Treatment is similar to CLL.

Watchful waiting

People with PLL who do not have any symptoms and whose cancer does not seem to be progressing do not need treatment right away. They are watched and treatment is started if the PLL begins to cause symptoms or it looks like the cancer is progressing.


Chemotherapy drugs used to treat CLL are also used to treat PLL. Unlike CLL, chlorambucil (Leukeran) by itself is not usually effective for treating B-PLL or T-PLL. PLL responds better when combinations of chemotherapy drugs are used. These combinations produce responses, but they may not be long-lasting. Some combinations that may be used are:

  • CVP – cyclophosphamide (Cytoxan, Procytox), vincristine (Oncovin) and prednisone (Deltasone)
  • CHOP – cyclophosphamide, doxorubicin (Adriamycin), vincristine and prednisone

Other chemotherapy drugs, called purine analogues, are often used to treat PLL and seem to be effective:

  • fludarabine (Fludara)
  • cladribine (2-CDA, Leustatin)
  • pentostatin (deoxycoformycin, Nipent)

Biological therapy

Monoclonal antibodies are a type of biological therapy that has been effective in treating certain types of NHL. These drugs may be used alone or in combination with chemotherapy to treat PLL.

  • alemtuzumab (Campath)
    • Alemtuzumab seems to be particularly effective in treating T-PLL. It may be used in people whose lymphoma is no longer responding to chemotherapy drugs like fludarabine.
  • rituximab (Rituxan)
    • Rituximab has not been used very much. Some studies have reported that it may be effective in treating B-PLL, especially in people who are not responding to other treatments.

Splenectomy or radiation therapy to the spleen

Removing the spleen with surgery (splenectomy) or giving external beam radiation therapy to the spleen may be used in some people with PLL who have very enlarged spleens. These measures are used to relieve pain or to control symptoms (palliative therapy).

Stem cell transplant

A stem cell transplant (SCT) is sometimes used to treat people with aggressive PLL. Many people with PLL are older or may not be in good health, so a SCT is often not a suitable option for them. However, it may be an effective option for younger people with PLL.

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