VII.B: Precursor Lymphoblastic Lymphoma

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VII.B.001

Precursor lymphoblastic lymphoma, T-cell type. Precursor lymphoblastic lymphoma, T-cell type. (A) Marrow section. Replaced with lymphoblasts with high nuclear:cytoplasmic ratio, small nucleoli, and irregular nuclear outlines. (B) Marrow touch preparation showing typical lymphoblast cytology: high nuclear:cytoplasmic ratio, inconspicuous nucleoli, irregular nuclear outlines. A few vacuoles are present in this case. (C) Marrow biopsy section with positive immunostain for terminal deoxynucleotidyl transferase (TdT) indicated by reddish brown nuclear stain. Some cases of very immature myeloid leukemias (AML-MO) may have a similar cytologic appearance and will be myeloperoxidase-negative on cytochemical staining. Precursor T-cell and precursor B-cell neoplasms can have similar morphologic features, although precursor T-cell cases are more likely to have convoluted or lobulated nuclei. Either one can express TdT, which indicates an immature lymphoid origin. Precursor Bcell neoplasms are defined by expression of surface CD19 and/or CD79a, CD10, and cytoplasmic CD22, with lack of surface kappa or lambda immunoglobulin light chain expression. Precursor T-cell neoplasms are defined by lack of surface CD3 expression, cytoplasmic co-expression of CD3, lack of surface T-cell receptors, and often show either dual lack of CD4 and CD8 or dual co-expression of CD4 and CD8, phenotypes that mimic the stages of immature thymocytes.

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VII.B.002

Acute lymphoblastic lymphoma. Precursor T-cell type. Seventeen-year-old male. Normal blood white cell count and differential count. No blast cells in the blood. (A and B) Film of a cytocentrifuge preparation of the cells from a needle aspiration biopsy of enlarged cervical nodes. Homogeneous population of lymphoblasts. Flow cytometry. (C) Abnormal cell population with increased forward angle light scatter. (D) Dual expression of T-cell markers CD3 and CD7. (E) Dual expression of surface CD4 and CD8. More than 95% of all cells had the latter phenotype. Other markers of an immature T-cell population were also present, including weak TdT, and sCDla, and cytoplasmic CD3. This dual CD4+/CD8+ phenotype is sometimes referred to as a “cortical thymocyte” phenotype, since it superficially mimics an intermediate stage of normal T-cell maturation that occurs in the cortex of the thymus.

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VII.B.003

Acute lymphoblastic lymphoma. Precursor T-cell type. Seventeen-year-old male with 4 days of intermittent fever and enlarged bilateral, non-tender lymph nodes that extended into the neck bilaterally. Chest x-ray shows a large mediastinal mass. Left image, P/A view. Right image, lateral view. Mass in the anterior mediastinum.