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Difficulty: Very hardPediatric Hematology and Oncology

Match the following pediatric hematologic malignancies with their characteristic molecular, cytogenetic, or immunophenotypic findings.

  • Pediatric B-cell Acute Lymphoblastic Leukemia (B-ALL)Hyperdiploidy (>50 chromosomes) or t(12;21) fusion; bone marrow aspirate shows lymphoblasts positive for TdT, CD10, and CD19.
  • Pediatric T-cell Acute Lymphoblastic Leukemia (T-ALL)Often presents with an anterior mediastinal mass; blasts are typically TdT-positive and universally express early T-cell markers such as CD2, CD3, and CD7.
  • Burkitt LymphomaTranslocation t(8;14) resulting in c-MYC overexpression; histology reveals a 'starry sky' pattern interspersed with tingible body macrophages.
  • Anaplastic Large Cell Lymphoma (ALCL)Translocation t(2;5) creating an NPM-ALK fusion protein; tumor cells are characteristically positive for CD30 and feature horseshoe-shaped nuclei.
  • Juvenile Myelomonocytic Leukemia (JMML)Hyperactivation of the RAS signaling pathway (e.g., PTPN11 mutations); characterized by profound in vitro hypersensitivity of myeloid progenitors to GM-CSF.

Answer

B-ALL matches CD10/CD19 positivity with t(12;21); T-ALL matches the mediastinal mass and CD2/CD3/CD7 expression; Burkitt Lymphoma matches the t(8;14) translocation and 'starry sky' histology; ALCL matches the t(2;5) NPM-ALK fusion and CD30 positivity; and JMML matches RAS pathway mutations with GM-CSF hypersensitivity.
Each pediatric malignancy has a unique defining signature. B-ALL is recognized by its CD10/CD19 positivity and t(12;21) or hyperdiploidy. T-ALL is uniquely associated with mediastinal masses and CD2/CD3/CD7 expression. Burkitt Lymphoma relies on the t(8;14) c-MYC translocation causing rapid proliferation ('starry sky'). ALCL is defined by t(2;5) NPM-ALK fusions and CD30+ hallmark cells. Finally, JMML is a distinct myeloproliferative disorder identified by RAS pathway mutations and diagnostic GM-CSF hypersensitivity.

Step-by-Step Solution

1
Identify the diagnostic hallmarks of Pediatric B-cell Acute Lymphoblastic Leukemia (B-ALL).
Matched with TdT, CD10, and CD19 positivity, alongside favorable cytogenetics like hyperdiploidy or t(12;21).
Recognizing the distinct surface markers and favorable cytogenetics separates B-ALL from other leukemias.
2
Identify the clinical and immunophenotypic presentation of Pediatric T-cell Acute Lymphoblastic Leukemia (T-ALL).
Matched with an anterior mediastinal mass and T-cell markers such as CD2, CD3, and CD7.
The anterior mediastinal mass (often compressing the SVC or airway) and T-cell surface antigens are primary distinguishing features for T-ALL.
3
Determine the genetic and histologic features of Burkitt Lymphoma.
Matched with the t(8;14) translocation causing c-MYC overexpression and a 'starry sky' pattern on histology.
The c-MYC translocation is the fundamental oncogenic driver of Burkitt Lymphoma, leading to extreme proliferation and high macrophage clearing activity.
4
Match Anaplastic Large Cell Lymphoma (ALCL) to its specific molecular abnormality.
Matched with the t(2;5) translocation producing the NPM-ALK fusion protein and CD30 expression.
The ALK fusion protein is the defining molecular feature of pediatric ALCL, presenting with large anaplastic cells.
5
Identify the underlying pathogenesis of Juvenile Myelomonocytic Leukemia (JMML).
Matched with hyperactivation of the RAS pathway and profound in vitro hypersensitivity of myeloid progenitors to GM-CSF.
JMML requires specific pathway mutations for diagnosis, making it clinically distinct from classic acute leukemias.

Key Concept

Molecular and immunophenotypic characterization of pediatric hematologic malignancies.
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Topics

Pediatric Hematology and Oncology

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