Hairy cell leukaemia

Hairy cell leukaemia (HCL) is a rare chronic B-cell leukaemia characterised by distinctive biological features and unusual sensitivity to treatment. The name of the disease is a reference to the distinctive appearance of the malignant cell (Figs 24.1 and 24.2).

Prolymphocytic leukaemia

Prolymphocytic leukaemia (PLL) may be connected with chronic lymphocytic leukaemia (p. 46), but it more often presents de novo and is best regarded as a distinct disease. The malignant cell is usually of B-lineage and is more mature than the B-CLL cell. Thus, in addition to characteristic B-cell antigens, the cells show a high density of surface immunoglobulin and clonal rearrangements of both heavy and light chain immunoglobulin genes. TP53 mutations are commonly found. Approximately 20% of cases are of T-cell lineage.

T-cell large granular lymphocyte leukaemia

T-cell large granular lymphocyte leukaemia (T-LGL) is a clonal disorder of cytotoxic T-lymphocytes. It is often associated with autoimmune disorders such as rheumatoid arthritis. The most common blood manifestation is severe chronic neutropenia although anaemia and thrombocytopenia may also occur. Patients can suffer from recurrent infections, ‘B symptoms’ such as fever and weight loss, and hepatosplenomegaly. Although the disorder is unequivocally a leukaemia rather than a reactive process, it is generally indolent with responses to immunosuppressive treatment.

Adult T-cell leukaemia lymphoma

Adult T-cell leukaemia lymphoma (ATLL) is a malignant disorder of relatively mature T-lymphocytes. It is rare but of great interest as it is conclusively caused by a virus. The majority of patients with ATLL have antibodies to HTLV-1 and definitive evidence for the aetiological role of this retrovirus has come from studies showing monoclonal integration of proviral DNA in the leukaemic cells.

The disease is mostly seen in areas endemic for HTLV-1, notably in parts of Japan and in the islands of the Caribbean. There is a long latent period from infection to overt disease and less than 5% of infected people actually develop ATLL. Patients most commonly present in the fifth decade and, as its name suggests, ATLL may behave as a leukaemia or a lymphoma. In the most acute form presentation is with a frank leukaemia. The malignant cells in the blood are pleomorphic but often have very irregular polylobulated nuclei. Even within the leukaemic group there is great heterogeneity with chronic and smouldering forms. In 25% of cases the disease is better described as a lymphoma as there is no demonstrable blood involvement. Despite the variability of the pathology there are well-defined clinical and laboratory features which should prompt consideration of the diagnosis, particularly in a person from an HTLV-1 endemic area (Table 24.1). In practice, lymphoma-type ATLL may be confused with other forms of T-non-Hodgkin’s lymphoma. Leukaemic ATLL must be distinguished from Sezary syndrome, a lymphoproliferative disorder with circulating T-cells and skin changes including erythroderma and exfoliative dermatitis.