T-cell prolymphocytic leukemia

• Peripheral blood:

  • High WBC count, most cases > 100 × 109/L

  • Common variant: intermediate-sized lymphocyte, high N/C ratio, round or irregular nuclear contour, moderately condensed chromatin, prominent central nucleoli, deeply basophilic cytoplasm with protrusions, no granules

  • Small cell variant: small lymphocyte with round to mildly irregular nucleus, clumped chromatin with inconspicuous nucleolus, scant basophilic cytoplasm

• Immunophenotype

  • CD2+, CD3+, CD5+, strongly CD7+, TCRαβ

  • CD4+/CD8− (60%), CD4+/CD8+ (15-25%), CD4−/CD8+ (10-15%)

  • TCL1+, CD26+, CD52+

  • Negative: NK-associated marker (CD16, CD56, CD57), and cytotoxic granule molecule (TIA-1, granzyme B)

• Genetics

  • TCRβ, TCRγ genes rearranged

  • Rearrangement of TCL1, TCL1β in inv(14)(q11;q32.1) or t(14;14)(q11;q32.1)

  • Rearrangement of MTCP1 in t(X;14)(28;q11)

  • Trisomy 8 or iso8q

  • Mutations in ATM at 11q23