WBC Disorders Lab
Learning objectives
- LO 1Describe normal hematopoiesis and the hormonal and environmental factors that support it.
- LO 2Outline the WHO classification of white blood cell disorders.
- LO 3Distinguish leukemia from lymphoma and explain where they overlap.
- LO 4Recognize the common signs and symptoms of hematologic neoplasms.
- LO 5Plan the workup of a patient with a hematologic disorder: lab and ancillary tests, and expected outcomes.
MAPThe workup, in order
LO 1Normal hematopoiesis
Q1. How does the family tree branch?
- Hematopoietic stem cell (CD34+) →
- Common myeloid progenitor → granulocytes, monocytes, RBCs, megakaryocytes/platelets
- Common lymphoid progenitor → B cells (marrow), T cells (thymus), NK cells
- Granulocytes: myeloblast → promyelocyte (primary/azurophilic granules) → myelocyte (secondary granules; last to divide) → metamyelocyte (kidney nucleus) → band → segmented neutrophil
Myelopoiesis
- Stem cell → each myeloid line
Q2. Which growth factors drive each line?
| Factor | Source | Drives |
|---|---|---|
| EPO | Kidney (hypoxia) | RBCs |
| TPO | Liver | Megakaryocytes → platelets |
| G-CSF | Macrophages, stroma | Neutrophils (filgrastim) |
| GM-CSF · M-CSF | T cells, macrophages | Granulocytes + monocytes · monocytes |
| IL-3 · IL-5 · IL-7 | T cells · Th2 · stroma | Early progenitors · eosinophils · lymphoid |
| Stem cell factor | Stroma | Stem cells, mast cells (KIT) |
Step 1
JAK2 sits under the EPO, TPO and G-CSF receptors → JAK2 V617F lets cells grow without the hormone (PV, ET, myelofibrosis).
Q3. What does a normal marrow and smear look like?
- Niche: stroma (fibroblasts, adipocytes, osteoblasts, endothelium), matrix, sinusoids; needs iron, B12, folate
- Site: adult = axial skeleton; fetus = yolk sac → liver/spleen → marrow
- Cellularity ≈ 100 − age (≈50% fat at 50); M:E ≈ 3:1; large multinucleated megakaryocytes
- A normal RBC is ≈ ⅔ the size of a small lymphocyte: use RBCs to call cells "small" vs "large"
- Differential: neutrophils 50–70% > lymphocytes 20–40% > monocytes 2–8% > eosinophils 1–4% > basophils <1%
Normal marrow
- ~50% cells, 50% fat (middle age)
Lymphocyte + neutrophil
- RBC ≈ ⅔ the lymphocyte
Memory tool
Differential order: "Never Let Monkeys Eat Bananas." Cellularity: 100 − age.
Trap
Normal adult marrow does contain some lymphocytes (~10–15%). What's abnormal is a lymphoid aggregate (especially paratrabecular) or sheets of one cell type.
ApplyLO 1 application question
A1A 70-year-old's marrow is 90% cellular. Is that normal?
LO 2WHO classification
Q1. How are WBC neoplasms grouped?
| Family | Defining idea | Examples |
|---|---|---|
| Myeloid neoplasms | ||
| Acute myeloid leukemia | ≥20% myeloblasts; maturation block | AML t(8;21), APL t(15;17) |
| Myelodysplastic | Ineffective, dysplastic; cytopenias; blasts <20% | MDS del(5q); monosomy 5, 7 |
| Myeloproliferative | Effective overproduction; tyrosine kinase mutations | CML (BCR-ABL), PV, ET, PMF (JAK2) |
| Lymphoid neoplasms | ||
| Precursor | Lymphoblasts, TdT+ | B-ALL, T-ALL / lymphoblastic lymphoma |
| Mature B | Mimic a B-cell stage | CLL/SLL, follicular, mantle, MZL, DLBCL, Burkitt, hairy cell, LPL, myeloma |
| Mature T/NK | Post-thymic T cells | Mycosis fungoides/Sézary, ATLL, ALCL |
| Hodgkin | Few RS cells, reactive background | Classic (4) and NLPHL |
WHO = morphology + immunophenotype + genetics + clinical: ancillary studies are required.
Step 1 — the two-question sort
(1) Lineage: myeloid (MPO, CD13, CD33, CD117) vs lymphoid (B: CD19/20; T: CD3). (2) Maturity: blasts (TdT, CD34) vs mature cells.
In-house exam
Chromosome losses in MDS: monosomy 5 and 7.
Q2. What terms do I need?
| Term | Meaning |
|---|---|
| Lymphadenopathy | Enlarged node(s); nonspecific |
| Hyperplasia | ↑ cells; in nodes by pattern: follicular (B zone), paracortical (T zone; EBV, phenytoin), sinus histiocytosis |
| Auer rod | Pink-red needle in myeloid blast cytoplasm (fused primary granules); AML, especially APL |
| Russell body | Cytoplasmic PAS+ Ig; myeloma |
| Dutcher body | Intranuclear Ig; Waldenström |
Q3. How do I tell reactive hyperplasia from follicular lymphoma?
| Reactive | Follicular lymphoma | |
|---|---|---|
| Follicles | Varied sizes, in cortex | Crowded, back-to-back, uniform, beyond capsule |
| Germinal centers | Polarized, tingible-body macrophages, mitoses | Monotonous, no polarity |
| Mantle | Intact | Thin/absent |
| BCL2 in GC | Negative | Positive |
| Clonality | κ and λ | Light-chain restricted |
ApplyLO 2 application question
A1A 20-year-old with fever, sore throat and tender nodes has a node biopsy showing an expanded T zone with immunoblasts. Diagnosis?
LO 3Leukemia vs lymphoma
Q1. How do leukemia and lymphoma differ?
| Leukemia | Lymphoma | |
|---|---|---|
| Origin | Bone marrow | Lymph nodes, lymphoid tissue, solid organs |
| Blood | Spill-over common; often high WBC | Usually not |
| Lineage | Myeloid or lymphoid | Lymphoid only (HL vs NHL; B vs T) |
| Tempo | Acute (blasts) vs chronic | Indolent vs aggressive |
| Presents as | Marrow failure ± leukocytosis | Mass / lymphadenopathy |
Memory tool
The name follows the location: same cells in marrow/blood = leukemia, in a node = lymphoma. Tumor cells in the blood → it's behaving as a leukemia.
Q2. Which diseases are both?
- CLL ↔ SLL
- ALL ↔ lymphoblastic lymphoma
- Sézary ↔ mycosis fungoides
- ATLL, Burkitt
- Myeloid sarcoma = AML as a mass
CLL, hairy cell and mycosis fungoides are leukemias; follicular, mantle and marginal zone are lymphomas, not leukemias.
Trap — WBC count
- High WBC ≠ leukemia: leukemoid reaction (left shift, high LAP, toxic granulation, Döhle bodies)
- Leukemia ≠ high WBC: aleukemic leukemia; hairy cell → pancytopenia
- Pancytopenia argues against an MPN
LO 4Signs and symptoms
Q1. How does the tumor's location produce symptoms?
Memory tool — marrow failure A-B-C
Anemia (fatigue) · Bleeding (platelets) · Contagion (neutrophils): "packed marrow, empty blood."
Step 1
Tender, rapidly enlarging node with fever → reactive. Painless, rubbery, progressive (>2 cm, supraclavicular, >4–6 weeks) → lymphoma → excisional biopsy.
Q2. How do the leukemias present?
| Acute leukemia | CML | CLL | Hairy cell | |
|---|---|---|---|---|
| Onset | Abrupt | Insidious | Insidious | Indolent, progressive |
| Blood | High WBC (blasts) with neutropenia | Very high WBC, all stages | High WBC, mature lymphocytes | Pancytopenia, hairy cells |
| Symptoms | Bleeding, unusual (fungal) infections | Organomegaly | Diffuse nodes | Splenomegaly |
| Course | Urgent | → AML or fibrosis | Not curable | BRAF; long remissions |
In-house exam
Hairy cell: circulating hairy cells, splenomegaly, pancytopenia.
LO 5Workup, ancillary tests and outcomes
Q1. What does each test answer?
| Test | Answers | Classic use |
|---|---|---|
| Smear | What cells? | Blasts, Auer rods, smudges, hairy cells, left shift, basophilia, rouleaux, dysplasia |
| Chemistry | Turnover, organs | LDH, uric acid (tumor lysis), Ca, creatinine, protein/albumin, β2-microglobulin |
| Marrow aspirate | Cell morphology | Differential, flow, cytogenetics |
| Marrow core | Architecture | Cellularity, fibrosis, infiltrates (paratrabecular aggregate) |
| Flow cytometry | Lineage, maturity, clonality | CLL (CD5/23), ALL (TdT), AML (CD13/33), hairy (CD103) |
| IHC | Markers in tissue | BCL2 follicles, cyclin D1, CD15/30, CD138 |
| Cytochemistry | Myeloid vs lymphoid | MPO (AML), esterase (monocytic), TRAP (hairy), LAP (low in CML) |
| Cytogenetics / FISH | Translocations | t(9;22), t(15;17), t(14;18), t(11;14), t(8;14), del(17p) |
| Molecular | Mutations, MRD | BCR-ABL, JAK2, BRAF, MYD88, FLT3, NPM1 |
| Protein studies | Monoclonal Ig | Myeloma, Waldenström, MGUS |
High yield
Excisional node biopsy beats fine-needle aspiration: it shows the pattern (follicular vs diffuse, Hodgkin background) and gives enough tissue for ancillary tests.
Q2. How do I sort the small B-cell lymphomas?
| Lymphoma | Pattern | CD5 | CD10 | CD23 | Cyclin D1 | Genetics |
|---|---|---|---|---|---|---|
| CLL/SLL | Diffuse, proliferation centers | + | − | + | − | Trisomy 12 (30%) |
| Lymphoplasmacytic | Diffuse | − | − | − | − | MYD88; IgM |
| Mantle cell | Diffuse, vaguely nodular | + | − | − | + | t(11;14) |
| Follicular | Follicular ± diffuse | − | + | −/+ | − | t(14;18) BCL2 |
| Marginal zone | Diffuse, interfollicular | − | − | +/− | − | Trisomy 18, t(11;18) |
Memory tool — fast sort
CD5+? → CLL (CD23+) or mantle (cyclin D1+). CD10+? → follicular. Neither? → marginal zone or lymphoplasmacytic (IgM spike = LPL).
Q3. What are the expected outcomes?
| Disease | Patient | Outcome |
|---|---|---|
| ALL | Child 2–10 | Kids ~90% cured; adults worse |
| AML | Adult ~65 | Remission 60–70%; transplant; APL excellent (ATRA) |
| CML | Middle-aged | Near-normal with TKIs; untreated → blast crisis |
| CLL · follicular · mantle | Older | Indolent, incurable (4–10 y · 7–10 y · 3–5 y); → DLBCL |
| DLBCL · Burkitt | Adults · kids | Aggressive but curable |
| Hairy cell | Older men | Long remissions (cladribine) |
| Hodgkin | Young + >50 | 75–90% curable early; late effects |
| Myeloma | ~70 | Incurable |
ApplyLO 5 application questions
A1A 5-year-old has fever, pallor, petechiae, leg pain and occasional blasts on smear. Next step?
A2A 62-year-old with pneumonia has WBC 30k of mature neutrophils with Döhle bodies and high LAP. CML?
LABSlide atlas
Method: (1) blood, marrow, node or organ? (2) cellularity / fat? (3) one cell type or a mix? (4) small vs large (compare with RBCs)? (5) special features: Auer rods, hairs, smudges, fibrosis, owl eyes, hof? (6) pattern: follicular, diffuse, paratrabecular?
Leukemias
ALL marrow
- ~100% uniform blasts → cytopenias
AML smear
- Big blasts, nucleoli, Auer rod
AML marrow
- Packed blasts, one megakaryocyte, no fat
CML smear
- Too many granulocytes, all stages
CML high power
- Myelocytes, bands, basophils, eosinophils
CLL in liver
- Portal tracts full of small lymphocytes
Hairy cell
- Hair-like projections
In-house exam
AML smear = blasts + Auer rods (lumpy blasts with small purple rods). Bundles of Auer rods → APL.
Lymph nodes and non-Hodgkin lymphoma
Normal node
- Capsule, sinus, follicles with germinal centers
Growth patterns
- Follicular vs nodular vs diffuse
Lymphoma, gross
- Fleshy tan nodes, little necrosis
Lymphoma in node
- Through capsule into fat
DLBCL
- Sheets of large cells, nucleoli
Paratrabecular aggregate
- Hugging trabecula → follicular
In-house exam
Lymphoid aggregates hugging bony trabeculae → follicular lymphoma. Fleshy enlarged nodes → NHL. Large cells in sheets: lymphoma vs carcinoma → IHC (CD45/CD20 vs keratin).
Hodgkin lymphoma
Nodular sclerosis
- Broad fibrous bands
Lymphocyte predominant
- Sea of small lymphocytes; popcorn cells
Lymphocyte depleted
- Many RS cells, few lymphocytes
Mixed cellularity
- Mixed cells; CD15 lights RS cells
Reed-Sternberg cell
- Binucleate, owl-eye nucleoli
Hodgkin in spleen
- Pale nodules
Hodgkin in liver
- White tumor spots (advanced stage)
High yield
Splenic masses are far more likely hematopoietic than metastatic carcinoma; >4 splenic nodules is an adverse factor in Hodgkin.
Plasma cell myeloma
Myeloma marrow
- Sheets of near-normal plasma cells
Myeloma aspirate
- Eccentric nuclei, hof, binucleate
Myeloma skull
- Punched-out lucencies
In-house exam
Punched-out skull → myeloma; IL-6 (from plasma + stromal cells) drives plasma cell proliferation. Guaranteed question.
IDName that slide
Slide 1
Slide 2
Slide 3
Slide 4
Slide 5
Slide 6
Slide 7
Slide 8
Slide 9
Slide 10
Slide 11
Slide 12
MCQExam-style questions
1A 3-year-old has 4 days of fever, gum bleeding and petechiae; WBC is 68,500/µL. What will the marrow show?
2An adult's smear shows large blasts with prominent nucleoli and pink needle-shaped cytoplasmic inclusions. These inclusions are:
3What is the expected marrow cellularity of a healthy 60-year-old?
4Which growth factor is made by the liver and drives platelet production?
5A marrow core shows a lymphoid aggregate lining a bony trabecula beside normal myeloid cells. Most likely diagnosis?
6A 58-year-old has a painless 3-cm supraclavicular node for 2 months. Best biopsy?
7A 66-year-old's node shows small B cells that are CD5+, CD23−, CD10−. Which confirms the diagnosis?
8A 62-year-old with pneumonia has WBC 30,000/µL of mature neutrophils, toxic granulation, Döhle bodies and high LAP. Diagnosis?
9Which pair is the same disease presenting as a leukemia or a lymphoma?
10Which cytokine drives plasma cell proliferation in myeloma?
11Pancytopenia argues against which diagnosis?
12A tissue mass shows sheets of large cells. Which IHC pair best separates lymphoma from carcinoma?
!Source notes
| Item | Lecture | Step 1 / standard references |
|---|---|---|
| Auer rods | Abnormal secondary granules | Fused primary (azurophilic) granules |
| AML blast cutoff | ≥20% | t(8;21), inv(16), t(15;17) = AML at any blast count |
| Marginal zone genetics | Trisomy 18, t(11;18) | Trisomy 3 (± 18); t(11;18) in MALT |
| MZL markers | CD23 "+/−", CD43 "−" | Key on CD5− and CD10− (CD43+ in a subset) |
| DLBCL cure | ~50% | ~60–70% with R-CHOP |
| Lymphocytes in marrow | "Adults should not have lymphoid cells in the marrow" | Normal marrow has ~10–15% lymphocytes; aggregates/sheets are abnormal |