T cell prolymphocytic leukaemia, T-PLL

Definition

An aggressive T-cell leukaemia composed of small to medium sized prolymphocytes with a post-thymic phenotype, involving the blood, bone marrow, lymph nodes, spleen and skin.

Synonyms

Epidemiology

Accounts for 2% of all small lymphocytic leukaemias of adults over 30 years.

Clinical features

Patients present with hepatosplenomegaly(splenomegaly in 73% of cases)1 and generalised lymphadenopathy(in 50% of cases)1 (this contrasts with the lack of lymphadenopathy in B-PLL). 20% have skin infiltration (in contrast with the lack of skin involvement in B-PLL). Pleural effusions may occur. The peripheral lymphocyte count is usually 100.109/l. Anaemia and thrombocytopenia are common. Serology for HTLV-1 is negative.

Macroscopic appearances

Spleens weigh up to 2.9 kg, heavier than those of T-cell large granular lymphocyte leukaemia. The cut surface is uniformly red and firm1.

Histopathology

The peripheral blood contains small to medium size lymphoid cells with nuclei which vary from round to irregular and even cerebriform. The cytoplasm shows protruding blebs. There is strong staining with alpha-naphthyl esterase in a Golgi distribution. The marrow contains similar cells.

The cases with skin involvement show a dense dermal infiltrate around appendages but without epidermotropism.

The spleen shows a dense infiltrate in the red and white pulp. The white pulp is disrupted and atrophic. There is prominent angioinvasion1. Neoplastic cells extend through the splenic capsule and into hilar fat. There are areas of fibrosis, haemorrhage and calcification. In addition to the neoplastic lymphocytes, there is an increase in macrophages (CD68-positive).

Lymph nodes show a dense infiltrate predominantly in a paracortical distribution. Prominent high endothelial venules are infiltrated by neoplastic cells.

Variant:

typical
small cell variant, 20% of cases
cerebriform variant, 5% of cases

Immunohistochemistry

CD1a	negative
CD2	positive1
CD3	membrane positive, may be weak
CD4	85% positive
CD5	positive1
CD7	positive
CD8	25% coexpress CD4 and CD8; this is almost unique to T-PLL
CD25	negative1
CD30	negative1
CD43	positive1
CD45	positive1
CD45RO	positive1
CD56	negative1
CD57	negative1
TCRb	positive1
ALK1	negative1
TRAP	negative1
DBA44	negative1
TdT	negative1

: fresh frozen tissue only

Cytogenetics

Up to 90% of cases show an inversion on chromosome 14, (14)(q11;q32)1 Idic (8q) and translocations at X(q28) also commonly occur1.

Differential diagnosis

Most lymphoid malignancies preferentially involve the white pulp.
Hairy cell leukaemia shows a B-cell immunophenotype, with positivity for DBA44 and TRAP, red cell lakes and atrophy or white pulp.
Hepatosplenic T-cell lymphoma presents in young males with gross splenomegaly, with diffuse involvement of the red pulp by cells that are negative for CD8 and perforin and show a gd phenotype.

Prognosis

Although the initial course may occasionally be indolent, this is an aggressive condition with a median survival of seven months1.

References

0 World Health Organization Classification of Tumours, Tumours of the haematopoietic and lymphoid tissues, IARC Press 2001.

1 Osuji N, Matutes E, Catovsky D, et al. Histopathology of the spleen in T-cell large granular lymphocyte leukemia and T-cell prolymphocytic leukemia: a comparative review. Am J Surg Pathol 2005; 29:935-41

This page last revised 24.9.2005.