Definition
Adult T cell leukemia/lymphoma (ATCL) is a T cell lymphoma with leukemic manifestations involving lymph nodes, skin, spleen and liver. The neoplastic circulating cells vary in size, but characteristically are large multilobulated lymphoid cells. They are T cells, nearly always T helper cells (CD 4 positive) and show aberrant expression of T cell antigens.
Sample Cases
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Epidemiology
HTLV1 is strongly associated with ATCL. ATCL is localized to the Caribbean, southeastern US, and most notably southern Japan. The prognosis is poor with most patients dying within 1-2 years.
Possible causes
The cause is unknown.
Morphology
These cells are predominantly medium to large cells with irregular, pleomorphic nuclei with prominent nucleoli. Mitotic figures may be present.
The CD45 vs SSC gating dot plot identifies a population of large cells (green population) and small lymphocytes (red population). The ATCL will fall in the larger cell region as they have bright CD45 and moderate to high SSC.
Aberrant expression of T cell antigens in ATCL with CD3 positive and CD7 negative antigen expression (CD3 +; CD7 + expected on normal T cells). The ATCL cells express CD 25 (the interleukin 2 receptor).
Below are selected example dual paramenter dot plots of a case of ATCL:
Genetics: TCR genes are clonally rearranged in most cases. Numerous chromosome abnormalities are usually seen.
There are two variants seen based on morphologic features: T-zone variant and the Lymphoepithelioid cell variant.
Flow cytometry immunophenotyping shows large cells CD45 bright and SSC moderate to high. The pan T cell markers are expressed, but aberrant phenotypes are common. CD4 is usually expressed and not CD8. CD30 and CD25 can be expressed in some cases.