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How do you differentiate erythrodermic mycosis fungoides and Sezary syndrome - is it primarily based on the burden of blood involvement of malignant cells?

Mycosis fungoides and Sezary syndrome are thought to be distinct genotypically and phenotypically. It is my understanding that Sezary syndrome typically arises de novo while erythrodermic MF progresses from patches > plaques > tumors more gradually. What are other ways to differentiate definitively between these entities?
2 Answers
Mednet Member
Mednet Member
Dermatology · University of Virginia School of Medicine
Answered on

You are correct: Sezary and erythrodermic MF are not the same things, and Sezary is erythroderma (defined as 80% BSA or more) right from the start. But our current definition of Sezary also requires Stage B2 blood involvement, and specifically that the sum of CD4+ CD7- and CD4+CD26 - cells is > 1000...

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Mednet Member
Mednet MemberInvited Expert
Dermatology · UT Southwestern School of Medicine
Answered on

Rather than the 1K marker which is often not reported on flow cytometry reports, there are 'proxy' percentages.

>30% of the LYMPHOCYTES (not of all the WBC) CD4+CD26- cells

OR

>40% of the LYMPHOCYTES (not all the WBC) CD4%CD7- cells

OR

CD4:CD8>10 with phenotypically abnormal cells (loss of other ea...

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