2025 – PAGE 279 – HEMATOLOGY & ONCOLOGY

ANTERIOR MEDIASTINAL MASS

An anterior mediastinal mass is another ONCOLOGIC EMERGENCY! It can cause respiratory failure or superior vena cava (SVC syndrome). The mass may be a lymphoma, ectopic thyroid tissue, or a thymoma (the most common tumor found in the anterior mediastinum).

• RESPIRATORY FAILURE may result from tracheal compression BELOW the vocal cords making it difficult to intubate. Do NOT give sedation to attempt intubation because you WILL lose the ability to maintain oxygenation in the patient.
• SVC SYNDROME is compression of the SVCby an anterior mediastinal mass. Symptoms include facial swelling, dusky color due to venostasis, weight loss, and night sweats due to the presence of a malignancy. SVC syndrome is most commonly due to a lymphomatous mass. Treat with steroids, radiation, and whatever the definitive treatment is for the anterior mediastinal mass.

RBC BASICS & SOME HEMOGLOBIN FACTS

(DOUBLE TAKE) CELL LIFE SPANS

The red blood cell (RBC) has a life span of about 120 days (about 4 months). Platelets live for about 10 days.

MNEMONIC: Imagine an EGG carton (12) that has RBCs in it. Alternatively, if you are worried that will make you think of 12 days instead of 120 days, imagine a CAR (4) with FOUR balloon-like RED BLOOD CELLS on the car instead of four wheels to remind you that RBCs live for 4 months.

MNEMONIC: Imagine going BOWLING (10) at a place that uses 10 PLATES instead of pins.

MNEMONIC: Bigger cell (RBC) = Bigger lifespan!

FETAL & ADULT HEMOGLOBIN STRUCTURE

• FETAL HEMOGLOBIN structure is made of 2 alpha chains and 2 gamma chains, denoted as α2γ2. The alpha chains have 4 alleles and the gamma chains have 2 alleles. Fetal hemoglobin is referred to as Hemoglobin F (Hgb F).
  • NEWBORNS: 50-80% of the circulating hemoglobin is fetal hemoglobin (Hgb F).
  • 6 MONTHS: 10% of the circulating hemoglobin is fetal hemoglobin (Hgb F).
  • 12 MONTHS: < 2% of the circulating hemoglobin is fetal hemoglobin (Hgb F).
• ADULT HEMOGLOBIN structure is made of 2 alpha chains and 2 beta chains. The alpha chains have 4 alleles and the beta chains have 2 alleles = a₁₂₃₄a₁₂₃₄b₁₂b₁₂. Note that “a” = alpha, “b” = beta. Normal adult hemoglobin is referred to A1.
  • THALASSEMIA: Alpha thalassemia refers to a mutation in an alpha chain allele. Beta thalassemia refers to a mutation in a beta chain allele.