Prolymphocytes (large [T] lymphocytes usually with prominent nucleoli) represent at least 50 percent of lymphocytes in the blood. They often have nuclear convolutions.
T-prolymphocytes characteristically express pan-T-cell markers: CD2, CD3, CD5, and CD7.
In the majority of cases, prolymphocytes express CD4 but not CD8 (i.e., malignant cell of T-helper cell origin). In occasional morphologically identical cases, CD4 may be weakly expressed or absent and CD8 may be weakly positive. CD52 is highly expressed and can be a target of therapy.
Inversion of chromosome 14 is the most common cytogenetic abnormality and is found in 80 percent of patients. The t(14;14) occurs in 10 percent of patients. Associated abnormalities of chromosome 8 (e.g., t(8;8)) are common as well. Several other chromosomes (e.g., 6, 11, 17) may also be abnormal.
Represents 20 percent of prolymphocytic leukemias; the remainder have a B-cell phenotype.
The male:female ratio is 1.5:1.
The tissue (e.g., lymphatic tissue) involvement and blood involvement coexist and are striking in both locations.
Most patients have generalized lymphadenopathy and hepatosplenomegaly with marrow replacement and lymphoma cells dominating the white cell count (usually >100 × 109/L).
Anemia and thrombocytopenia are nearly always evident at diagnosis.
Skin involvement occurs in approximately 20 percent of patients.
Serology for the human lymphocytotropic virus-1 is negative.
The clinical course is usually rapid. Median survival is less than 1 year.
No standard chemotherapeutic treatment program has been developed. For example, cyclophosphamide, hydroxydaunorubicin (doxorubicin), vincristine (Oncovin), prednisone (CHOP) therapy does not produced long-term remissions.
Pentostatin and cladrabine can induce responses in approximately 40 percent of patients; but, complete remissions are infrequent (~10%) and long-term responses (>1 year) are uncommon.
Alemtuzamab, a humanized monoclonal antibody against CD52, given three times weekly, has induced good responses in over 50 percent of patients.
Allogeneic hematopoietic stem cell transplantation can induce a long-term remission of the disease.
Occasional patients may have a chronic course of a few years but then evolve to a rapidly progressive phase.