DIP Episode 81 - USMLE Step 1 Hematology Review Part 3 (Oncology)

Source / episode info

• Episode: 81
• Title: Divine Intervention Episode 81 – USMLE Step 1 Hematology Review Part 3 (Oncology)
• Published: 2019-02-21
• Source: Episode page

One-liner

This episode reviews key myeloproliferative neoplasms (MDS, PMF, PV, ET, CML), the spectrum of plasma cell dyscrasias (MGUS, MM, Waldenstrom's), and critical high-yield concepts including tumor lysis syndrome, hyperviscosity, and bone remodeling pathways.

High-yield summary

• Myelodysplastic Syndromes (MDS): Characterized by ineffective hematopoiesis due to early apoptosis of precursors in the bone marrow, leading to peripheral pancytopenia and macrocytic anemia (MCV > 100). Look for dysplastic features like "pseudo-Pelger-Huet" bodies.
• Primary Myelofibrosis (PMF): A myeloproliferative neoplasm characterized by bone marrow fibrosis due to megakaryocyte-derived cytokines (e.g., TGF-). Classic findings include tear-drop shaped reticulocytes/megakaryocytes (dacrocytes) and massive hepatosplenomegaly.
• Multiple Myeloma (MM): Defined by the presence of monoclonal protein (M protein) and bone marrow plasmacytosis, often presenting with CRAB criteria: Calcium elevation, Renal failure, Anemia, Bone pain/lesions.
• Polycythemia Vera (PV): The most common myeloproliferative neoplasm associated with a JAK2 mutation; classically presents with aquagenic pruritus and can cause Budd-Chiari syndrome (hepatic vein thrombosis).
• CML Staging: Progression is defined by the loss of differentiation: Chronic Phase -> Accelerated Phase (blasts < 20%) -> Blast Crisis (loss of differentiation, becomes AML).

Learning objectives

• Differentiate between Myelodysplastic Syndromes (MDS) and Myeloproliferative Neoplasms (MPN).
• Recognize the classic clinical and laboratory findings associated with Primary Myelofibrosis (PMF), Polycythemia Vera (PV), and Essential Thrombocythemia (ET).
• Master the staging of Chronic Myeloid Leukemia (CML) based on blast percentage and differentiation ability.
• Apply the CRAB criteria to diagnose Multiple Myeloma (MM) and distinguish it from MGUS or Waldenstrom's Macroglobulinemia.
• Understand the pathophysiology and management of acute hematologic emergencies like Tumor Lysis Syndrome (TLS) and hyperviscosity syndrome.

Board exam buzzwords

Rapid review table

Board-speak -> diagnosis

Differential diagnosis / distinguishing features

Myeloproliferative Neoplasms

Management pearls

• TLS Management: Aggressive hydration is paramount. Use Allopurinol or Rasburicase to prevent uric acid nephropathy. Monitor for hyperkalemia/hypocalcemia and provide continuous cardiac monitoring.
• MM Diagnosis: The combination of elevated M protein (SPEP) and bone marrow plasmacytosis, plus evidence of end-organ damage (CRAB), confirms active MM.
• CML Treatment: Use a Tyrosine Kinase Inhibitor (TKI) that targets the BCR-ABL fusion kinase (e.g., Imatinib). The drug name often ends in "-nib."
• PMF Management: Bone marrow transplant is curative, but initial management focuses on symptom control and reducing thrombotic risk using JAK inhibitors like Ruxolitinib.

Don't miss

Integration & clinical reasoning

• Bone Remodeling Axis: Estrogen maintains bone health by promoting OPG synthesis, which sequesters RANKL. Menopause leads to decreased estrogen -> decreased OPG -> increased RANKL activity -> osteoporosis. Bisphosphonates mimic this protective effect.
• MPN Thrombosis Risk: High thrombocytosis (ET) or high RBC mass (PV) increases the risk of microvascular thrombosis and bleeding/ischemia.
• TLS & Chemotherapy: The release of intracellular phosphate (\text{PO}_4^{3-}), potassium (\text{K}^+), and nucleic acids leads to hypocalcemia, hyperkalemia, and uric acid nephropathy, respectively.

OMM / COMLEX integration

• For unstable/emergent pathology (e.g., severe bleeding, acute renal failure from TLS): Standard emergency management takes priority over OMT. Stabilization protocols must be followed first.
• TLS Management: The need for aggressive hydration and monitoring of electrolytes (\text{K}^+, \text{Ca}^{2+}) is critical in any setting of massive cell death (e.g., severe sepsis, blast crisis).

Concept connections / cross-references

• For detailed information on the bone remodeling axis (RANKL/OPG) and osteoporosis treatment: [Cross-reference to a podcast episode covering endocrine pharmacology].
• For comprehensive review of general hematology principles including peripheral smear interpretation: [Cross-reference to an earlier Hematology Review episode].

High-yield association table

Key terms glossary

Study optimization

Question pattern recognition

• The "Most Common" Trap: Be aware that while PV is the most common MPN, CML (Philadelphia chromosome) and MM are also highly tested and must be differentiated correctly.
• Morphology vs. Function: Do not confuse the morphological findings of MDS (dysplasia/apoptosis) with the functional overproduction seen in MP Ns (PV/ET).
• The "Best Answer" Trap: When diagnosing a myeloproliferative neoplasm, always consider if the patient has an associated complication (e.g., PV -> Budd-Chiari syndrome; ET -> thrombosis risk).

Test yourself

Common mistakes to avoid

Common traps