CLL: B versus T versus PLL, and all things lymphocyte

[Guest guest]

I wanted to recap and further explain some of what has been said regarding this

topic.

The important thing to remember is that it was not until the 80s that we had a

reliable, and easy method for differentiating T cells from B cells. Under the

microscope they appear identical. The classification scheme that was used until

1994 did not even distinguish T cell from B cell lymphomas (The National Cancer

Institute Working Group). In 1994, the REAL (Revised European American

Lymphoma) Classification separated CLL into T-CLL and B-CLL. (It also combine

CLL and SLL.)

As diagnostic methods improved, it became clear that T-CLL really is a mix of

different tumors, and that a true CLL diagnosis requires a B cell phenotype.

Previous cases of " T-CLL " were better described as mycosis fungoides, ATLL, etc.

This is when B-CLL became CLL. It is important to not get confused the CLL of

2002 WHO (World Health Organization) Classification with the CLL of the 1982 NCI

Working Group (NCI-WG). The NCI-WG CLL is a term applied to all patients with

an increased lymphocyte count that contain mature appearing lymphocytes. This

included a mix of T cell, B cell, and NK cell malignancies.

In the WHO Classification, CLL refers to a lymphoma that is specifically B cell.

Prolymphocyte leukemia is a different entity and can be either B or T cell in

type. B-PLL can arise new or from CLL and is characterized by havnig the cells

appear with more cytoplasm and irregular nuclei. T-PLL is different in that it

can contain cells that appear like normal T cells.

It is important to remember that CLL patients are allowed to have prolymphocytes

(up to 55%), so having some does not mean a PLL transformation.

Rick Furman, MD