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Toronto Notes 2019 Basics of Hematology
WHITE BLOOD CELLS
• lymphocytes
■ comprise 30-40% of WBCs; great variation in “normal” lymphocyte morphology
• neutrophils
■ normally, only mature neutrophils (with 3-4 lobed nucleus) and band neutrophils (immediate
precursor with horseshoe-shaped nucleus) are found in circulation
■ hypersegmented neutrophil: >5 lobes suggests megaloblastic process (B12 or folate deficiency)
■ left shift (increased granulocyte precursors)
◆ seen in leukemoid reactions: acute infections, pregnancy, neonates, hypoxia, shock, and
myeloproliferative neoplasms (CML, MF)
• blasts
■ immature, undifferentiated precursors; associated with acute leukemia, MDS, and G-CSF (growth
Hematology H5
factor that stimulates neutrophil production) use
Table 4. Abnormal White Blood Cells on Film
Left Shift
Refers to an increase in granulocyte precursors in the peripheral smear (myelocytes, metamyelocytes, promyelocytes, blasts). If present, implies increased marrow production of granulocytes (e.g. inflammation, infection, G-CSF administration, CML)
The presence of predominantly blasts in
the peripheral smear without cells between mature neutrophil and blast suggests clonal cell disorder (MDS, acute leukemias)
If >20% of the total WBC differential consists of blasts, this is acute leukemia and is a medical emergency
Appearance
Reed-Sternberg Cell
Smudge Cell
Auer Rod
Atypical Lymphocyte
Definition
Giant, multinucleated B-lymphocyte, (classic 'owl-eye' morphology)
Lymphocytes damaged during blood film preparation indicating cell fragility
Cytoplasmic inclusions that form long needles in the cytoplasm of myeloblasts
Pale blue cytoplasm following RBC edges with pink granules
Associated Conditions
Primarily Hodgkin lymphoma, also seen in some non-Hodgkin lymphoma, CLL, and EBV infection
CLL and other lymphoproliferative disorders
Pathognomonic in EBV infection
Pathognomonic for acute myeloid leukemia (AML)
Viruses (particularly EBV) T-cell large granular lymphocyte leukemia (T-LGL)
EBV = Epstein-Barr virus; CLL = chronic lymphocytic leukemia
Illustrations: Ayalah Hutchins and Merry Shiyu Wang 2012 and Danielle Sayeau 2017
PLATELETS
• small,purple,anuclearcellfragments
Bone Marrow Aspiration and Biopsy
• sites:posterioriliaccrest,sternum • analyses:mostoftendonetogether
■ aspiration: takes a fluid marrow sample for cellular morphology, flow cytometry, cytogenetics, molecular studies, and microbiology (C&S, acid-fast bacilli, and PCR)
◆ note: differential diagnosis for a “dry tap”: MF, hairy cell leukemia, bone marrow infiltration
■ biopsy: takes a sample of intact bone marrow to assess histology (architecture) and
immunohistochemistry
■ only aspirates, not biopsies, can be obtained from the sternal site
Indications
• unexplainedCBCabnormalities
• diagnosisandevaluationofinfiltratingcancers:plasmacelldisorders,leukemias,andsolidtumours • diagnosisandstagingoflymphomaorsolidtumours
• evaluateironmetabolismandstores(goldstandard,butrarelydone)
• evaluatesuspecteddepositionandstoragedisease(e.g.amyloidosis,Gaucher’sdisease)
• evaluatefeverofunknownorigin,suspectedmycobacterial,fungal/parasiticinfections,or
granulomatous disease
• evaluateunexplainedsplenomegaly
• confirmnormalbonemarrowinpotentialallogeneichematopoieticcelldonor
Important Considerations
• consultahematologistpriortoconductingabonemarrowbiopsyonapatientwithaninherited(e.g. hemophilia, vWF disease) or acquired (e.g. DIC, anticoagulant therapy, coagulopathy of liver disease, and severe thrombocytopenia) bleeding diathesis to determine if pro-hemostatic therapy is indicated pre-procedure
• donotperformabonemarrowbiopsyifthereisevidenceofinfectionoverthetargetedskinsite