Leukemia
The article addresses leukemia, which is uncommonly seen by anatomical pathologists. It is a subset of hematopathology.
Lymphoma is discussed in the lymphoma article, and overlaps somewhat with leukemia as the clear distinction between the two is historical (see below).
Historical classification:[1]
- Leukemia = involves bone marrow +/- peripheral blood.
- Classic presentation: infection, bleeding, anemia.
- Lymphoma = discrete mass(es), usu. lymph node.
- Classic presentation: non-tender lymph nodes
Definition
All of the following:[2]
- Morphologic abnormalities.
- >20% blasts or recurrent cytogenetic abnormality.
Some recurrent cytogenetic abnormalities:
- t(8;21).
- inv(16).
- t(15;17).
Histomorphologic overview
| Disease/Feature | Blast size | Auer rods | Granulation of cytoplasm |
| Acute myeloid leukemia (AML) | larger | present | present |
| Acute lymphoid leukemia (ALL) | smaller † | none | absent or present |
† should be easy to remember as smALL people, i.e. kids, get this type of acute leukemia.
Algorithms
There is a nice set of algorithms from D. Arber - that were presented at the 2009 USCAP.
Clinical factors in classification
Clinical are important in the classification of leukemia.
- Hx of myelodysplastic syndrome?
- Chemotherapy?
- Down syndrome?
Leukemia classification
Acute myeloid leukemia (AML):
- AML.
- AML with recurrent cytogenetic abnormalities.
- AML from MDS.
- AML in the setting of Down syndrome.
Acute lymphoid leukemia (ALL):
- B cell.
- B cell with recurrent cytogenetic abnormalities.
- T cell.
Specific diagnoses
Acute myeloid leukemia
- Abbreviated AML.
General
- Adults.
Exclusions for this diagnosis:
- Prior MDS.
- Down syndrome.
Microscopic
Features:
- Auer rods present
- Cytoplasmic granularity.
- Large cells.
Image:
Molecular
- Must exclude all the recurrent cytogenetic abnormalities - see below.
AML with recurrent cytogenetic abnormalities
Acute myeloid leukemia with t(8;21)
- t(8;21)(q22;q22).[3]
IHC:
- CD34+, CD13+, MPO+ (cytoplasm), CD33+ (weak).
- CD56+, CD117+.
- Usu. assoc. with a bad prognosis.
Flow cytometry:
- CD19+, PAX5+, CD79a +/-.
Acute myeloid leukemia with inv(16)
- inv(16)(p13.1q22).[4]
- Associated with myeloid sarcoma.
Microscopic:
- Blast count usu. ~20% (low).
- Eosinophilic granules.
- Used to be classified as "M4" with eosinophilia.
IHC:
- CD2+ -- common.
Acute myeloid leukemia with t(15;17)
- t(15;17)(q22;q12).
Comes in two flavours.
Microscopic (Hypergranular or typical APL):
- Bean-shaped nucleus or bilobed nucleus.
- Buddles of Auer rods - known as "Faggot cells".
Microscopic (Microgranular or hypogranular APL):
- Bilobed nuclei with nuclear overlap. (???)
- Absence of granules on light microscopy.
IHC:
- CD2+, CD34+/-, CD56+/-.
- CD34-, HLA-DR-.
- CD33+, CD13+/-, CD117+ (weak), CD56+/-.
Clinical:
- Assoc. with DIC.
- Treatment: ATRA.
Variants:
- t(11;17) -- ATRA doesn't work.
- t(17;17) -- ATRA doesn't work.
- t(5;17). (???)
Acute myeloid leukemia with t(9;11)
- t(9;11).
Microscopic:
- Monoblastic morphology. (???)
- Myelomonocytic morphology. (???)
Clinical:
- +/-DIC.
- Usu. children.
IHC:
- CD33+, CD65+, CD4+, HLA-DR+.
- CD34+. (???)
- CD13+. (???)
See also
References
- ↑ Mitchell, Richard; Kumar, Vinay; Fausto, Nelson; Abbas, Abul K.; Aster, Jon (2011). Pocket Companion to Robbins & Cotran Pathologic Basis of Disease (8th ed.). Elsevier Saunders. pp. 314. ISBN 978-1416054542.
- ↑ D. Good. 21 March 2011.
- ↑ Berger, R. (1994). "Translocation t(8;21)(q22;q22): cytogenetics and molecular biology.". Nouv Rev Fr Hematol 36 Suppl 1: S67-9. PMID 8177719.
- ↑ Lu, CM.; Murata-Collins, JL.; Wang, E.; Siddiqi, I.; Lawrence, HJ. (Dec 2006). "Concurrent acute myeloid leukemia with inv(16)(p13.1q22) and chronic lymphocytic leukemia: molecular evidence of two separate diseases.". Am J Hematol 81 (12): 963-8. doi:10.1002/ajh.20716. PMID 16917916.