ID of T lymphoblasts and T-ALL Flashcards
What is the definition of T-ALL ?
- malignant neoplasm of immature T cells
- Characteristic immunophenotype by flow:
- positive:
- CD2, cCD3, CD5 and bright CD7
- majority: TdT, CD34 and or CD1a
- negative
- sCD3 and HLA-DR
- usually either dual CD4/CD8 positive or dual negative
- rare cases are either CD4 or CD8
- positive:
- Other markers that may be positive:
- CD10, CD43, CD71 and CD123
- HLA-DR+ cases can be CD33+ as well
What are the immunophenotypic categories
of T-ALL ?
- Pro-T
- Pre-T
- Cortical T
- Mature (medullary) T cells
What are the immunophenotypes of pro-T and pre-T ALLs ?
-
Pro-T-ALL:
- CD7+, cCD3, CD34+/-
- negative for: sCD3, CD1a, CD2, CD5, CD4, and CD8
-
Pre-T-ALL:
- cCD3+, CD7+, CD34+/-, CD2+ and/or CD5+, TdT+
- negative for: sCD3, CD1a
- CD4/CD8– or CD4/CD8++
What is the immunophenotype of Cortical T
and Mature (medullar) T-ALL ?
-
Cortical T-ALL:
- cCD3+, CD2+, CD1a+, sCD3+/-, CD4/CD8++
- negative: CD34
-
Mature (medullar) T cells:
- sCD3+, CD4+ or CD8+
- negative for: CD1a
What are the WHO defined T-ALL categories
and how are they defined ?
- Early T-ALL
- CD1a-, sCD3-
- Thymic T-ALL
- CD1a+, sCD3-
- Mature T-ALL
- CD1a-, sCD3+
What is an early T-cell precursor T-ALL
(ETP-ALL) ?
- this phenotype is similar to the early T cell precursors of the thymus
- absence of CD1a
- negative for CD4 and CD8
- negative CD5
- at least 25% of the lymphoblasts are positive for myeloid/stem cell markers
- CD11b, CD13, CD33, CD34, CD65, CD117, and/ or HLA-DR
- Rare cases of ETP-ALL
- may be partially dim for CD5 ( <75% of lymphoblasts) and or CD4+
How is early T-ALL differentiated from ETP-ALL ?
What is the differential diagnosis for
T-ALL ?
- Mature (peripheral) T cell neoplasma vs. T-ALL
- Thymocytes vs. T-lymphoblastic lymphoma
- Indolent T lymphoblastic proliferation
- Acute undifferentiated leukemia
- Mixed phenotype AML
How is T-ALL differentiated from a mature T cell neoplasm ?
- expression of blastic markers (TdT and CD34) as well as CD1a favors T-ALL
- aberrant expression of myeloid antigens (CD13 and/or CD33) is seen in a subset of T-ALL
- Dim to moderate expression of CD45 is in T-ALL
- mature T cells are usually bright for CD45
- IMP: T-PLL may be negative for CD45
- peripheral T cell neoplasms (mature)
- more likely to lose CD7 and retain CD2 and CD5
- opposite for T-ALL
What two mature T cell neoplasms are
usually negative for CD5 ?
- EATL - enteropathy associated T cell lymphoma
- often CD8+
- rare cases CD4-/CD8-
- Hepatosplenic T cell lymphoma
- usually CD4-/CD8-
- rare cases CD8+
Expression of what markers favors a T-ALL over
a more mature T cell neoplasm ?
- positive for CD10 or CD117
- lack of TCR
What mature T cell neoplasms are frequently positive
for CD10 ?
- Angioimmunoblastic T cell lymphoma (AITL)
- Nodal, peripheral T-cell lymphoma with T cell follicular helper phenotype
What diagnostic consideraton do dual CD4 and CD8 positive
T cells bring about ?
- dual positivity is rare in the peripheral blood
- suspicious for an immature T cell neoplasm
- in the mediastinum it is more difficult
- Thymomas and thymic hyperplasia always have dual CD4 and CD8 positive populations
- mediastinal T-ALL cannot be based on the presence of CD4/CD8 co-expression
What is the T cell pattern frequently seen in
thymomas or thymic hyperplasia ?
- always CD4 and CD8 positive
- variable expression of sCD3
- majority of small T cells
- note: large T cells are negative for sCD3
- CD10
- small, mature T cells are CD10-
- larger, immature T cells (negative for sCD3) are positive for CD10
What disease are indolent T lymphoblastic proliferations
associated with ?
- Castleman disease
- various types of carcinoma
- Follicular dendtritic cell tumors
- AITL
- predilection for involvement of the oropharynx/nasopharynx
- long-term clinical course with frequent recurrences but no evidence of systemic disease
