Chapter 15: HEMATOLOGY & ONCOLOGY

NOTE: The ABP content specifications have consistently said that about 2.5% of the exam will cover hematologic disorders. In general, there tends to be a much greater focus on non-malignant processes.

PEDIATRIC LEUKEMIAS

(DOUBLE TAKE) DEFINITIONS/PEARLS: Leukemias and lymphomas are both LYMPHOblastic disorders of T and B cells.

• LEUKEMIA: Bone marrow biopsy shows > 25% blasts
• LYMPHOMA: Bone marrow biopsy shows < 25% blasts, and NONTENDER lymphadenopathy is present somewhere (neck, mediastinum, groin, etc.).
• CELL LINES IMAGE: www.pbrlinks.com/PEDIALEUKEMIAS1

PEARL: Leukemia—Look for increased leukocytes (WBCs) in the blood and marrow. The primary leukemia in kids is ALL. It’s doubtful that you would be tested on anything else.

ACUTE LYMPHOCYTIC LEUKEMIA (ALL) (AKA ACUTE LYMPHOBLASTIC LEUKEMIA)

Remember, LYMPHoid cells are T and B cells. Acute Lymphocytic Leukemia (ALL) is usually a B-cell (AKA plasma cell) issue. It may be due to a translocation, t(4;11). ALL is the most common pediatric malignancy and has a great cure rate if caught in time. As the name suggests, it presents ACUTELY. Symptoms may include fever, organomegaly (liver or spleen), or joint pain. Either the leukocyte count (WBC) will be very high (>50) with a high LYMPHOCYTE predominance, or the child may present with pancytopenia and a low WBC. The pancytopenia occurs due to marrow failure if the child presents later in the disease process. Patients go into remission quickly after chemotherapy but continue to get intrathecal chemotherapy to prevent a relapse. If they relapse, they will need a bone marrow transplant.

PEARL: If given the results of a bone marrow biopsy, look for > 25% blasts to diagnose a leukemia.

PEARL: If the patient has a pancytopenia, they might only give you a low WBC in the labs section. You will have to figure out the rest by circling words like “pallor” and “easy bruising.” Also, the pancytopenic picture could look like aplastic anemia, so look for organomegaly to help you diagnose ALL.

MNEMONIC: ALL kind of looks like 4;LL, which should help you think of t(4;11).

ACUTE MYELOID LEUKEMIA (AML)

Acute myeloid leukemia (AML) may present with similar symptoms to ALL. The WBC will be high, but RBCs and platelets may be low due to marrow infiltration. Infections can occur because the leukemic WBCs are defective. You may be shown a myeloblast. If so, look for AUER RODS.

IMAGE: www.pbrlinks.com/MYELOIDLEUKEMIA1

CHRONIC MYELOGENOUS LEUKEMIA (CML) & CHRONIC LYMPHOCYTIC LEUKEMIA (CLL)

Chronic Myelogenous Leukemia (CML or Chronic Myeloid Leukemia) and Chronic Lymphocytic Leukemia (CLL). If by some rare chance they refer to a Philadelphia chromosome, choose CML. The Philadelphia chromosome is a t(9;22) translocation.

MNEMONIC: Philadelphia = t(P;22)

PEARL: CML and CLL tend to be adult diagnoses, so these are low-yield topics, EXCEPT for the fact that they can probably be excluded from any answer choices.