Six new cases of prolymphocytic leukemia with heterogeneous prognosis. Clinical and immunologic features, light microscopy, and ultrastructural findings.

The clinical features and diagnostic evaluation of six patients affected by prolymphocytic leukemia (PLL), are described. Some of the cases deviate from a relatively uniform and aggressive clinical course of the disease entity. An actuarial survival analysis of 60 cases gathered from the literature and the authors' experience indicate that the cases showing the most prolongated evolution may reach 30% of the total. The different aggressiveness in the clinical course of these patients does not depend on the efficiency of the therapies applied. The percentage of prolymphocytes (PL) in peripheral blood throughout the clinical course was variable and not depending on the treatments used. This fact, in conjunction with (1) the presence of cellular types deviated from the typical PL and detected both at optical and ultrastructural levels and (2) the existence of cases of PL with minimal splenomegaly and leukocyte counts of less than 50 × 109/liter, could lead to an underdiagnosis of PLL and hinder the actual cognition of the natural medical history of the disease.