T-Cell Prolymphocytic Leukemia

Definition

T-cell prolymphocytic leukemia (T-PLL) is an aggressive disease characterized by a proliferation of small to medium-sized lymphocytes with a postthymic phenotype usually involving blood, bone marrow, lymph nodes, spleen, and skin. This leukemia was first described by Catovsky and colleagues in reference to a patient who presented with cytologic features similar to B-cell prolymphocytic leukemia (B-PLL), but the cells were shown to bind sheep erythrocytes (E-rosette positive). In 1986, Matutes and coworkers published a more detailed report comparing morphologic and clinical characteristics of 29 T-PLL and 33 B-PLL cases and defining the immunophenotype as consistent with mature T cells. In 1987, the same group reported an association of T-PLL with inv(14)(q11q32) and trisomy for 8q.

Epidemiology

T-PLL represents approximately 2% to 3% of all T-cell disorders but accounts for up to one third of mature T-cell malignancies with a leukemic presentation. This leukemia occurs mainly in older adults (median age 61 years) and more often in men (male-to-female ratio approximately 2 : 1). An increased frequency has been found in patients with ataxia telangiectasia, an autosomal recessive disorder caused by loss of heterozygosity at 11q22-23 (mutated ATM gene). Patients with ataxia telangiectasia develop T-PLL at a younger age (26 to 43 years). A single sporadic pediatric case has been reported.

Clinical Features

Most T-PLL patients present with general symptoms: sweating, malaise, weight loss, or fever. The median duration of symptoms is 2 months before diagnosis. In most patients, a high white blood cell count (>100 × 10 ⁹ /L in 72%), sometimes with extreme hyperlymphocytosis, splenomegaly (79%), lymphadenopathy (46%), and enlarged liver (39%) are found. One fourth of patients have skin lesions at diagnosis, mainly maculopapular rash, nodules, or (more seldom) erythroderma. In 15% to 30% of patients, mainly those with high WBC counts, serous effusions are found at diagnosis or may also develop later in the course of the disease. Central nervous system involvement is rare. Thirty percent to 50% of patients present with anemia (hemoglobin <100 g/L) or thrombocytopenia (<100 × 10 ⁹ /L), or both. Usually there is no neutropenia or monocytopenia. Hyperuricemia and increased levels of lactate dehydrogenase are common. Other liver function tests may be mildly elevated, whereas serum immunoglobulin and renal biochemistry are normal. Although serum from most Western T-PLL patients has tested negative for human T-lymphotropic virus (HTLV) types 1 and 2, in some Japanese patients DNA samples contained an HTLV-1 Tax sequence. A single case of Epstein-Barr virus–positive T-PLL has been reported.

Morphology

Typical T-PLL cells in the peripheral blood are medium-sized lymphocytes with a high nuclear-to-cytoplasmic ratio and deeply basophilic cytoplasm without granules, often showing protrusions ( Box 32-1 ; Fig. 32-1, A ). Ultrastructural studies show numerous ribosomes, polyribosomes, and profiles of rough endoplasmic reticulum, accounting for the cytoplasmic basophilia. Nuclei are often irregular, with numerous short indentations, and they have moderately condensed chromatin and prominent nucleoli. Cytochemical staining for α-naphthyl-acetate esterase shows a characteristic dotlike pattern.

Box 32-1

Major Features of T-Cell Prolymphocytic Leukemia

You're Reading a Preview

Become a Clinical Tree membership for Full access and enjoy Unlimited articles

Become membership

If you are a member. Log in here