A 10-year-old boy with trisomy 21 arrives for his annual check-up with his pediatrician. His parents explain that over the past week, he has been increasingly withdrawn and lethargic. On examination, lymph nodes appear enlarged around the left side of his neck; otherwise, there are no remarkable findings. The pediatrician orders some routine blood work. These are the results of his complete blood count: WBC 30.4 K/μL RBC 1.6 M/μL Hemoglobin 5.1 g/dL Hematocrit 15% MCV 71 fL MCH 19.5 pg MCHC 28 g/dL Platelets 270 K/μL Differential: Neutrophils 4% Lymphocytes 94% Monocytes 2% Peripheral smear demonstrates evidence of immature cells and the case is referred to hematopathology. On flow cytometry, the cells are found to be CALLA (CD10) negative. Which of the following diseases is most associated with these clinical and cytological findings?

Precursor T-cell acute lymphoblastic leukemia/lymphoma

Precursor B-cell acute lymphoblastic leukemia/lymphoma

A 53-year-old man comes to the physician for recurring fever and night sweats for the past 6 months. The fevers persist for 7 to 10 days and then subside completely for about a week before returning again. During this period, he has also noticed two painless lumps on his neck that have gradually increased in size. Over the past year, he has had an 8.2-kg (18.1 lbs) weight loss. Two years ago, he had a severe sore throat and fever, which was diagnosed as infectious mononucleosis. He has smoked a pack of cigarettes daily for the past 10 years. He does not drink alcohol. His job involves monthly international travel to Asia and Africa. He takes no medications. His temperature is 39°C (102.2°F), pulse is 90/min, respirations are 22/min, and blood pressure is 105/60 mm Hg. Physical examination shows 2 enlarged, nontender, fixed cervical lymph nodes on each side of the neck. Microscopic examination of a specimen obtained on biopsy of a cervical lymph node is shown. Which of the following additional findings is most likely present in this patient?

Acid fast bacilli in the sputum

Anti-viral capsid antigen IgG and IgM positive

A 5-year-old boy presents to his pediatrician with weakness. His father observed that his son seemed less energetic at daycare and kindergarten classes. He was becoming easily fatigued from mild play. His temperature is 98°F (37°C), blood pressure is 90/60 mmHg, pulse is 100/min, and respirations are 20/min. Physical exam reveals pale conjunctiva, poor skin turgor and capillary refill, and cervical and axillary lymphadenopathy with assorted bruises throughout his body. A complete blood count reveals the following: Leukocyte count: 3,000/mm^3 Segmented neutrophils: 30% Bands: 5% Eosinophils: 5% Basophils: 10% Lymphocytes: 40% Monocytes: 10% Hemoglobin: 7.1 g/dL Hematocrit: 22% Platelet count: 50,000/mm^3 The most specific diagnostic assessment would most likely show which of the following?

Bone marrow biopsy with ≥ 20% lymphoblasts

Fluorescence in situ hybridization analysis with 9:22 translocation

Peripheral blood smear with > 50% lymphoblasts

Flow cytometry with positive terminal deoxynucleotidyl transferase staining

Fluorescence in situ hybridization analysis with 12:21 translocation

A 37-year old man is being evaluated due to a recent history of fatigue that started 3 weeks ago. The patient presents with a history of HIV, which was first diagnosed 7 years ago. He has been on an antiretroviral regimen and takes it regularly. His CD4+ count is 350 cells/mm3. According to the patient, his partner passed away from a "blood cancer", and he is worried that his fatigue might be connected to a similar pathology. The physician clarifies that there is an increased risk for HIV patients to develop certain kinds of lymphomas. Which one of the conditions below is the patient more likely to develop based on his medical history?

Extranodal marginal zone lymphoma

An inconsolable mother brings her 2-year-old son to the emergency room after finding a large amount of bright red blood in his diaper, an hour ago. She states that for the past week her son has been having crying fits while curling his legs towards his chest in a fetal position. His crying resolves either after vomiting or passing fecal material. Currently, the child is in no apparent distress. Physical examination with palpation in the gastric region demonstrates no acute findings. X-ray of the abdominal area demonstrates no acute findings. His current temperature is 36.5°C (97.8°F), heart rate is 93/min, blood pressure is 100/64 mm Hg, and respiratory rate is 26/min. His weight is 10.8 kg (24.0 lb), and height is 88.9 cm (35.0 in). Laboratory tests show the following: RBC count 5 million/mm3 Hematocrit 36% Hemoglobin 12 g/dL WBC count 6,000/mm3 Mean corpuscular volume 78 fL What is the most likely underlying embryological cause predisposing to this condition?

Failure of the vitelline duct to close

Failure of the vitelline duct to open

Elevated anti-mitochondrial antibodies

Problem with bilirubin conjugation

An 18-month-old boy is brought to the doctor’s office for evaluation of abdominal pain. The boy looks emaciated and he is now significantly below his growth chart predicted weight. The family history is non-contributory. The vital signs are unremarkable. On physical examination, a non-tender mass is felt in the upper part of the abdomen. A magnetic resonance image (MRI) scan of his abdomen demonstrates a mass in his right adrenal gland. Biopsy of the mass demonstrates an abundance of small round blue cells. With this biopsy result, which 1 of the following findings would confirm the diagnosis?

Elevation of vanillylmandelic acid in the urine

MRI showing the intrarenal origin of the mass

Radiograph of the bone showing the presence of lytic bone lesion with periosteal reaction

A 2-year-old boy is brought to the physician because of progressive difficulty breathing and a productive cough for the past 2 days. During the past 6 months, he has had recurrent episodes of pneumonia treated with antibiotics. He has not gained weight in this time period. His temperature is 38.5°C (101.3°F), pulse is 130/min, respirations are 18/min, and blood pressure is 100/60 mm Hg. Auscultation of the lungs shows decreased breath sounds over the right lung fields. Ocular examination shows periorbital subcutaneous bleeding and bulging of both eyes. His leukocyte count is 16,000/mm3. An x-ray of the chest shows a right-sided opacity and a collapsed right lung. An MRI of the chest shows a heterogeneous mass in the posterior mediastinum that compresses the heart and the great vessels to the left side. Further evaluation is most likely to show which of the following?

Overexpression of the N-myc oncogene

Unregulated B-cell proliferation in the mediastinum

Acid-fast bacteria on sputum microscopy

Increased lymphoblast count in the bone marrow

Autoantibodies against nicotinic acetylcholine receptors

A 7-year-old girl is brought to the physician by her mother because of a 2-week history of generalized fatigue, intermittent fever, and progressively worsening shortness of breath. Physical examination shows pallor, jugular venous distention, and nontender cervical and axillary lymphadenopathy. Inspiratory stridor is heard on auscultation of the chest. The liver is palpated 3 cm below the right costal margin. Her hemoglobin concentration is 9.5 g/dL, leukocyte count is 66,000/mm³, and platelet count is 102,000/mm³. An x-ray of the chest shows a mediastinal mass. A bone marrow aspirate predominantly shows leukocytes and presence of 35% lymphoblasts. Which of the following additional findings is most likely in this patient?

Positive myeloperoxidase staining

Lymphomas in pediatric population for USMLE Step 2 CK: High-Yield Pediatrics Lessons

Lymphoma Basics - The Great Divide

Two main types: Hodgkin Lymphoma (HL) and Non-Hodgkin Lymphoma (NHL).
Distinction is crucial for staging, treatment, and prognosis.

Hodgkin's Lymphoma: Reed-Sternberg cell (H&E stain)

Hodgkin Lymphoma:
- Characterized by pathognomonic Reed-Sternberg (RS) cells.
- Spreads contiguously (node-to-node).
- Typically presents with localized, non-tender lymphadenopathy.
Non-Hodgkin Lymphoma:
- More common in children < 15 years.
- Spreads non-contiguously and hematogenously.
- Often presents with extranodal disease (e.g., abdominal mass).

⭐ Unlike adult lymphomas, pediatric lymphomas are overwhelmingly aggressive (high-grade) and disseminated at diagnosis.

Hodgkin Lymphoma - The Orderly Owl

Epidemiology: Bimodal age distribution (15-30 yrs & >55 yrs); adolescent peak is key in pediatrics. Strong association with Epstein-Barr Virus (EBV).
Clinical Presentation:
- Painless, firm, rubbery lymphadenopathy (commonly cervical, supraclavicular).
- Spreads contiguously (orderly) to adjacent lymph node chains.
- B Symptoms: Unexplained fever >38°C, drenching night sweats, weight loss >10% over 6 months.
Diagnosis: Lymph node biopsy is essential.
- Pathognomonic finding: Reed-Sternberg (RS) cells.
- RS cells are large, binucleated cells with prominent eosinophilic nucleoli, giving an "owl-eye" appearance.

Reed-Sternberg cells with "owl-eye" appearance

⭐ Nodular Sclerosis is the most frequent histological subtype in the pediatric and adolescent population.

Non-Hodgkin Lymphoma - The Wild Bunch

⭐ Burkitt lymphoma is the most common type of pediatric Non-Hodgkin Lymphoma.

Represents ~60% of childhood lymphomas. More common in males. Characterized by rapid, aggressive growth and extranodal spread.

Clinical Presentation: Depends on subtype. Abdominal pain/mass, jaw involvement, lymphadenopathy, or mediastinal compression (SVC syndrome).
Diagnosis: Biopsy is essential. Staging is done using the St. Jude/Murphy Staging system.
Treatment: Aggressive multi-agent chemotherapy leads to high cure rates (>80%).

Subtype	Key Features	Common Site(s)	Genetics
Burkitt Lymphoma	Fastest growing human tumor. "Starry sky" histology. Associated with EBV.	Abdomen (ileocecal), Jaw	t(8;14) c-myc gene
Lymphoblastic	T-cell origin (~90%). Clinically similar to T-ALL.	Anterior Mediastinum	-
Large Cell (ALCL)	Anaplastic Large Cell Lymphoma. "Hallmark" cells.	Skin, Nodes, Bone	t(2;5) ALK gene

Staging & Strategy - The Battle Plan

Staging Systems:
- Hodgkin Lymphoma (HL): Ann Arbor system.
- Non-Hodgkin (NHL): St. Jude/Murphy system is preferred; better for extranodal disease.

⭐ St. Jude/Murphy staging is crucial for Burkitt Lymphoma, as it separates resectable (Stage I/II) from unresectable (Stage III) abdominal disease.

Treatment Principles:
- Backbone: Systemic, multi-agent chemotherapy.
- Radiation: Used selectively for bulky disease or sanctuary sites to minimize long-term effects.

High‑Yield Points - ⚡ Biggest Takeaways

Non-Hodgkin Lymphoma (NHL) is far more common in childhood than Hodgkin Lymphoma.

Hodgkin Lymphoma classically shows a bimodal age distribution and is defined by pathognomonic Reed-Sternberg cells.

Burkitt Lymphoma, a high-grade B-cell NHL, is strongly associated with EBV and shows a "starry sky" pattern on histology.

Lymphoblastic Lymphoma frequently presents with a supradiaphragmatic (mediastinal) mass and can overlap with T-ALL.

Staging systems differ: Ann Arbor for Hodgkin vs. St. Jude/Murphy for NHL.

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