APL Flashcards
What is the difference in expression of CD15 in normal vs. leukemic promyelocytes?
- leukemic promyelocytes typically express low to absent CD15
What is the immunophenotype of APL?
- CD13 heterogeneous
- CD33 strong and uniform
- CD117 heterogeneous
- MPO positive
- Negative for: CD34 and HLA-DR
- CD15 low to absent
- CD11a and CD18 low to absent
- CD133 (myeloid progenitor antigen) negative
What are the differences of the immunophenotype in the microgranular variant of APL?
- may have lower SSC similar to normal blasts
- variable expression of CD34
- CD2 is often positive
The expression of CD2 in the microgranular variant of APL has been associated with what?
- leukocytosis
- increased occurrence of thrombotic events
- shorter complete remission duration (described in some studies)
Are there any differences in the immunophenotype of therapy-related APL or APL with variant translocations?
- No
What is CD56 expression by APL associated with?
- seen in only a subset of APLs (~15%)
- associated with a poor prognosis
What other types of blast morphology (non APL) have been described in association with a negative CD34 and HLA-DR?
- non-APL AML morphology: cup-like nuclear indentations
- often have normal cytogenetics and contain mutations of NPM1 and FLT3
What are some immunophenotypic similarities of APL to monocytic leukemias ?
- high levels of CD33 expression and positivity for CD64
How can APL be immunophenotypically differentiated from a monocytic leukemia?
- APL shows bright expression of MPO and negative HLA-DR
- Monocytic leukemias should be the opposite
After therapy, immunophenotypes of APL may change. What are some changes that may be seen occasionally?
- upregulation of CD11b, CD11c and CD158
- immunophenotype shows differences from normal promyelocytes
- CD15 may be decreased as compared to normal
What can be seen in APL at relapse?
- similar morphology
- relatively increased expression of CD34 and HLA-DR with decreased CD13
