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 about 25% of all cases of adult ALL. T-LBL constitutes ~85% of cases of lymphoblastic lymphoma and most cases are adolescent. There is a case report of concurrent T-lymphoblastic leukaemia/lymphoma and invasive thymoma2.

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

	immunoreactivity	notes
TdT	positive	nuclear positivity is unique to LBL
CD1a	variable
CD2	variable
CD3	usually positive, cytoplasmic	the only marker considered lineage-specific
CD4	variable	frequently co-expressed with CD8
CD5	variable
CD7	usually positive
CD8	variable	frequently co-expressed with CD4
CD10	may be positive
CD13	often positive
CD33	often positive
CD79a	positivity has been observed	12/23 cases positive on frozen section1
CD117	rarely positive

: 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.

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

2 Friedman HD, Inman DA, Hutchison RE, et al. Concurrent invasive thymoma and T-cell lymphoblastic leukemia and lymphoma. A case report with necropsy findings and literature review of thymoma and associated hematologic neoplasm. Am J Clin Pathol 1994; 101:432-7

This page last revised 16.12.2002.