PVSG and WHO vs European Clinical, Molecular and Pathological Criteria for prefibrotic myeloproliferative neoplasms

Table 5 Grading of reticulin fibrosis and myelofibrosis

Grading[78,79]	Grading of MF[80]	Description of RF and RCF in MF as a secondary event in MPN
Normal RF-0	MF 0	No reticulin fibers, occasional individual fibers or focal areas with tiny amount of reticulin fiber network
RF 1 Slight increase	MF 0	Fine reticulin fiber network throughout much of section and no course reticukin fibers
RF 2 Moderate increase	MF 1	Diffuse fine reticuline network with focal collections of thick course reticulin fibers and no collagenisation
RF 3 = RCF Marked increase	MF 2	Diffuse and dense increase in reticulin with extensive intersections, and presence of collagen fibers and no or minor osteosclerosis
RF 4 = RCF and O OS Dry tap	MF 3 Sclerotic	Diffuse and dense reticulin with with coarse bundles of collagen associated with significant O

MF: Myelofibrosis; RF: Reticulin fibrosis; RCF: Reticulin/collagen fibers; MPN: Myeloproliferative neoplasms; O: Osteosclerosis.