NK-lymphoblastic leukemia/lymphoma

Question 1

What is the issue with this

disease entity ?

Answer 1

• very difficult entity to define
• many of the cases in the literature previously that were CD56 positive have been found to be BPDCN

Question 2

What is true about NK cell

progenitors when they develop ?

Answer 2

• they express no specific markers OR they express markers that overlap with T-ALL
  
  • CD7, CD2
  • even CD5 can be positive
  • cCD3 epsilon
• CD16
  
  • more mature marker of NK cells
  • rarel ever expressed in NK cell leukemia

IMP: difficult to distinguish between T-ALL and NK-cell tumors

Question 3

What are other relatively specific markers

for NK cells ?

Answer 3

• relatively specific and expressed on NK cell progenitors
  
  • CD94
  • CD161
  • unfortunately these are uncommonly tested

Question 4

In what circumstance can a diagnosis of NK

lymphoblastic leukemia/lymphoma be considered ?

Answer 4

• as of now this is a provisional entity
• can consider this diagnosis IF:
  
  • cells express CD56
  • immature T associated markers: CD7, CD2, cCD3
  • lack of B and myeloid antigens
  • TR and IG genes are in the germline configuration
  • BPDCN has been excluded