T-LGL leukemia represents only 2-3% of mature lymphocytic leukemias. Classically patients present with neutropenia and splenomegaly. Most patients don’t die from the leukemia itself, but accompanying diseases/cytopenias. The peripheral blood LGL count is usually between 2-20x10e9/L. THere is a significant gray-zone of uncertainty between what constitutes a benign population of LGLs and a neoplastic process (possibly an immune response that turns neoplastic??).
Features
- Pathophysiology is NOT well understood
- STAT3 mutated in approximately 1/3rd of cases (rarely STAT5B)
- LGL count >2,000/μL (cases with <2,000/μL can be diagnosed if all other criteria are consistent with T-LGL leukemia
- “All other criteria” are not well-described
- Cases that resemble T-LGL but lack surface CD3 (sCD3) are classified in the NK-cell disorders.
Characteristic Immunophenotype
Stain
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Comment
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Positive
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Usually Negative. A subset of cases may express CD4. CD4 + cases have been associated with an underlying malignancy (~30% of cases).
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+/- (May have diminished or lost expression)
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+/- (May have diminished or lost expression)
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|
Usually Positive
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Granzyme_B
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Usually Positive
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TIA-1
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Positive
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CD57
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Positive (>80% of cases)
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Usually negative
|
References
Swerdlow SH, Campo E, Harris, NL, Jaffe ES, Pileri SA, Stein H, Thiele J (Eds): WHO Classification of Tumours of Haematopoietic and Lymphoid Tissues (Revised 4th edition). IARC: Lyon 2017
Hematopathology. [edited by] Jaffe, ES. 1st. ed. Elsevier, Inc. © 2011.