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
|
Comment
|
|
Positive
|
|
|
Usually Negative. A subset of cases may express CD4. CD4 + cases have been associated with an underlying malignancy (~30% of cases).
|
|
|
+/- (May have diminished or lost expression)
|
|
|
+/- (May have diminished or lost expression)
|
|
|
Usually Positive
|
|
|
Granzyme_B
|
Usually Positive
|
|
TIA-1
|
Positive
|
|
CD57
|
Positive (>80% of cases)
|
|
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.