Precursor T Lymphoblastic Leukemia / Lymphoma
Definition
- Neoplasm of T-lineage lymphoblasts which may form lymphomatous masses and/or involve the blood and bone marrow
Alternate/Historical Names
- Acute lymphoblastic leukemia, FAB L1 and L2
Diagnostic Criteria
- May present as leukemia, lymphoma, or both
- Lymphoma characteristically presents in anterior mediastinum (less commonly lymph nodes), < 25% lymphoblasts in bone marrow
- Leukemia if > 25% lymphoblasts in bone marrow or lack of mass lesion
- Histology is high grade
- Tissue biopsies are often effaced
- Tingible body macrophages may impart “starry sky appearance”
- Cytology is quite variable
- Small to medium-sized round blasts with high N:C ratio, inconspicuous nucleoli, and finely stippled chromatin
- Large blasts with convoluted nuclei, abundant clear cytoplasm, and prominent nucleoli
- Range of blast sizes in any one patient is typical
- Precursor T immunophenotype
