Precursor T lymphoblastic lymphoma / leukaemia

A neoplasm of lymphoblasts committed to T-cell lineage. Most cases involve blood and bone marrow (T lymphoblastic leukaemia, T-ALL), some present with primary nodal or extanodal tissue deposits (T lymphoblastic lymphoma, T-LBL).

Epidemiology

T-ALL is predominantly a disease of adolescents and occurs more commonly in males. T-ALL constitutes ~25% of all cases of adult ALL. T-LBL constitutes ~85% of cases of lymphoblastic lymphoma and most cases are adolescent.

Clinical features

T-ALL usually presents with a leukocytosis and often with a large mass in the mediastinum or elsewhere. There is a relative sparing of bone marrow haematopoiesis. T-LBL often presents with a mediastinal mass, less often with involvement of peripheral lymph nodes, skin,liver, spleen, Waldeyer's ring, CNS or gonads.

Histopathology

• Lymph nodes usually show complete effacement, less often with paracortical infiltration. There may be a "starry sky" pattern. Mitotic figures may be numerous.

• Some cases of T-LBL show eosinophilia and myeloid hyperplasia. This is associated with t(8;13)(p1.2;q11-22).

Immunohistochemistry

†: fresh frozen tissue only

Differential diagnosis

• Lymph nodes and extranodal tissue: in children, Burkitt lymphoma. In adults, blastoid variant of mantle cell lymphoma Positivity for TdT readily distinguishes LBL.

• Myeloblastic infiltration is positive for chloroacetate esterase, myeloperoxidase and lysozyme.

References

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

¹Hashimoto, M., Y. Yamashita, et al. (2002). "Immunohistochemical detection of CD79a expression in precursor T cell lymphoblastic lymphoma/leukaemias." J Pathol 197(3): 341-7.

This page last revised 16.12.2002.

©SMUHT/PW Bishop