DIP Episode 203 - Leukemia’s and Lymphoma’s for the USMLE Step 2CK and Step 3 Exams

Source / episode info

• Episode: 203
• Title: Divine Intervention Episode 203 – Leukemia’s and Lymphoma’s for the USMLE Step 2 CK and Step 3 Exams.
• Published: 2020-01-15
• Source: Episode page

One-liner

This episode reviews the classic presentations of hematologic malignancies, differentiating leukemias from lymphomas, detailing specific types (CLL, CML, Hodgkin), and reviewing myeloproliferative disorders like Polycythemia Vera and Myelodysplastic Syndrome.

High-yield summary

• Leukemia vs. Lymphoma: Leukemia often presents with peripheral blood abnormalities (e.g., marked leukocytosis or pancytopenia); lymphoma typically presents with localized lymphadenopathy, and the CBC may be normal.
• CLL Hallmark: Chronic Lymphocytic Leukemia (CLL) is characterized by absolute lymphocytosis, recurrent bacterial infections due to impaired B-cell function, and the presence of smudge cells on the peripheral smear.
• Hodgkin Lymphoma: The classic finding is the presence of Reed-Sternberg cells; it classically affects young adults/elderly (bimodal distribution) and is positive for CD15 and CD30 markers. Prognosis correlates with lymphocyte count (lymphocyte-rich > lymphocyte-depleted).
• CML Hallmark: Chronic Myeloid Leukemia (CML) involves the Philadelphia chromosome ({t}(9;22)), creating the {BCR-ABL} fusion protein, and is treated with a Tyrosine Kinase Inhibitor (TKI) like imatinib.
• Myeloproliferative Disorders: Polycythemia Vera (PV) involves elevated hematocrit/erythrocytosis due to JAK2 mutation; the primary treatment is phlebotomy to reduce blood volume and prevent hyperviscosity.
• MDS Hallmark: Myelodysplastic Syndrome (MDS) can present with peripheral cytopenias, often associated with a pseudo-Pelger-Huët anomaly (bi-lobed nucleus in neutrophils) and may mimic myeloproliferative disorders.

Learning objectives

• Differentiate the typical clinical presentations (CBC vs. physical exam) of leukemia versus lymphoma.
• Identify the characteristic findings and associated translocations for major leukemias (CLL, CML, AML).
• Recognize the classic signs and management principles for myeloproliferative disorders (PV, ET, PMF).
• Understand the immunophenotype and prognostic factors in Hodgkin Lymphoma.
• Differentiate between Myelodysplastic Syndrome (MDS) and Myeloproliferative Disorders (MPD).

Board exam buzzwords

Rapid review table

Board-speak -> diagnosis

Differential diagnosis / distinguishing features

Myelodysplastic Syndrome (MDS) vs Myeloproliferative Disorder (MPD)

Hodgkin Lymphoma vs Non-Hodgkin Lymphoma

Management pearls

• For Polycythemia Vera (PV), the initial and most critical intervention is phlebotomy to reduce blood volume and prevent hyperviscosity syndrome.
• CML requires treatment with a Tyrosine Kinase Inhibitor (TKI), such as imatinib, which targets the \text{BCR-ABL} fusion protein.
• In suspected CLL, monitor for signs of infection; while no specific cure exists, managing infections and monitoring lymphocyte counts is key.
• For MDS, treatment often involves supportive care and addressing cytopenias, as it can progress to AML.

Don't miss

Integration & clinical reasoning

• Hematopoiesis and Genetics: Understanding the specific translocations (\text{t}(9;22), \text{t}(15;17), \text{t}(8;14)) is crucial, as these genetic abnormalities drive the malignant proliferation in various hematologic cancers.
• Immunodeficiency: CLL represents a functional B-cell immunodeficiency despite high circulating lymphocytes, leading to increased susceptibility to bacterial infections (often encapsulated organisms).
• Cytokine Signaling: The JAK2 mutation in PV highlights how specific mutations can constitutively activate signaling pathways, driving uncontrolled proliferation of blood cells.

OMM / COMLEX integration

• Acute/Unstable Management: In any suspected acute myeloproliferative crisis or severe pancytopenia, standard emergency management (transfusion support, infection control) takes absolute priority over OMT.
• Myeloid Crisis Recognition: Recognizing the signs of marrow failure (pancytopenia, bleeding risk) is critical for immediate stabilization and blood product replacement before considering specific diagnoses like MDS or AML.

Concept connections / cross-references

• For detailed review of the general principles of hematopoiesis and bone marrow function, see [Episode 10].
• Understanding lymphadenopathy and systemic symptoms (fevers, night sweats) is crucial for differentiating malignancy types, as discussed in [Episode 201].

High-yield association table

Key terms glossary

Study optimization

Question pattern recognition

• The "Best Answer" Trap: Questions often test the most classic finding (e.g., smudge cells for CLL, RS cells for HL), even if other findings are present.
• Differential Diagnosis Overlap: Be prepared to distinguish between MDS and MPD based on whether the primary issue is dysplasia/ineffective marrow or overproliferation/hyperviscosity.
• Genetic Association: Linking a specific translocation (e.g., \text{t}(9;22)) directly to its associated malignancy (CML) is extremely high yield.

Test yourself

Common mistakes to avoid

Common traps