Primary Hematopoietic and Lymphoid Tissue ›› Thymus ›› Abnormal

T-cell Lymphoblastic Leukemia/Lymphoma (T-ALL)*


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› Microscopic Features:

• 3-4x larger than a mature RBC
• High nuclear to cytoplasmic ratio
• Round Nucleus with immature chromatin (not clumped)
• Prominent nucleoli
• Cytoplasm is scant, light blue in color and lacks granules

› Normal % blood-PB, marrow-BM, lymphoid tissue-LN:

• PB: None
• BM: None
• LN: None

› May Resemble:

• Myeloblast [Compare]
• Pronormoblast [Compare]
• Immature B-cell (hematogone) [Compare]
• Monoblast [Compare]
• Prolymphocyte
• Reactive lymphocyte [Compare]

› Differential Diagnoses:

If in blood, bone marrow or tissue: T-Lymphoblastic leukemia/lymphoma (T-ALL) B-Lymphoblastic leukemia/lymphoma (B-ALL) AML

› Classic Immunophenotype:

• CD3+ (cytoplasmic)
• CD7+
• TdT+
• CD1a (variable)
• CD2 (variable)
• CD5 (variable)
• CD4 (variable)
• CD8 (variable)

› Cartoon Image:


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› Misc:

• Can arise from thymus (Anterior Mediastinum). Remember the mnemonic for Anterior Mediastinal lesions/masses: 4 Ts (Thymoma, Terrible Lymphoma such as T-lymphoblastic lymphoma, Thyroid neoplasms, and Teratoma or other germ cell neoplasms)