T-cell prolymphocytic leukaemia: does the expression of CD8+ phenotype justify the identification of a new subtype? Description of two cases and review of the literature.

T-cell chronic lymphocytic leukaemia (T-CLL) has recently been reclassified under the heading of T-cell prolymphocytic leukaemia (T-PLL) because of its unfavourable clinical course, independently of the morphologic features. This rare neoplasm usually shows CD4+/CD8- phenotype. Herein we report on two cases of T-PLL with CD8 expression that correspond to a possible variant of the disease first proposed by Hui et al. in 1987. These cases presented with malignant cells showing immunophenotypic features that can be easily identified and distinguished from other peripheral T-cell leukemias. However, the total number of cases studied is inadequate for defining a discrete clinico-pathologic entity with characteristic clinical features and cytogenetical abnormalities. An international collaboration in which tissue from similar cases is referred to a central pathologist for immunophenotyping and cytogenetical study, and clinical data are centrally compiled, may assist in defining this rare malady as a discrete clinico-pathologic entity.