Subclassification of Erythroleukemia

 

Classification	Correlation
M6A	traditional French-American-British (FAB) M6 category
M6B	pure erythroleukemia
M6C

from Mazzella 1998

 

total nucleated cellularity in bone marrow differential = 100% =

= (percent erythroid precursors) + (percent nonerythroid precursors)

 

pronormoblasts as percent of total erythroid precursors =

= (percent pronormoblasts in differential count) / (percent total erythroid precursors in differential count) * 100%

 

myeloblasts as percent of total nonerythroid precursors =

= (percent myeloblasts in differential count) / (percent total nonerythroid precursors in differential count) * 100%

 

ratio of pronormoblasts to myeloblasts =

= (percent pronormoblasts in differential count) / (percent myeloblasts in differential count)

percent erythroid precursors in total differential	percent myelo-blasts in non-erythroid cells	percent pronormo-blasts in total erythroid cells	Classification
>= 50%	>= 30%	< 30%	M6A
>= 50%	< 30%	>= 30%	M6B
>= 50%	>= 30%	>= 30%	M6C
>= 50%	< 30%	< 30%	myelodysplasia

 

General features of the different subtypes:

(1) M6B and M6C show more cytogenetic aberrations, proliferation markers and ringed sideroblasts than M6A.

(2) M6B shows a decreased ability to obtain remission following chemotherapy.

(3) While chemotherapy can achieve remissions in M6C, relapse occurs much sooner than in M6A.

 

Survival is affected by the ratio of pronormoblasts to myeloblasts at diagnosis, with a rapid decline in survival as the ratio increases (increasing pronormoblasts, decreasing myeloblasts).

 

Classification	Survival
M6A	30.1 +/- 29.5 months
M6B	3.15 +/- 4.2 months
M6C	10.5 +/- 12.7 months

Mazzella 1998