Aims The diagnosis of primary myelofibrosis (PMF) strongly relies on the bone marrow biopsy findings, but a report model has not been standardised. Our aim was to establish general recommendations for bone marrow evaluation and standardised reporting in a case suspicious of PMF.

Methods The Delphi method was employed to obtain expert consensus. An advisory panel of 10 leading members identifies a total of 37 haematopathology experts to participate. The first Delphi round included a questionnaire with three main groups of items: minimal clinical and laboratory data considered necessary before reporting, minimal descriptive aspects to record and main histological differential diagnosis. The final report content was based on consensus obtained after the second Delphi round.

Results The minimal data considered necessary were age, splenomegaly, haemoglobin, leucocyte and platelet counts, differential blood cell count, leucoerythroblastic blood picture, lactate dehydrogenase (LDH) level, BCR-ABL and JAK2 mutational status, reticulin stain and the internal control for the reticulin staining. The minimal descriptive aspects to report were cellularity, osteosclerosis, megakaryocytic morphology and localisation, dense megakaryocytic clusters, quantity of granulocytic precursors, grade of myelofibrosis in a scale of 4, and a proposed final diagnostic approach. The entities to be considered for differential diagnosis were mainly the other classical chronic myeloproliferative neoplasms.

Conclusions The Delphi method is a robust tool to determine essential information to be included in a pathology report. A standardised good-quality histopathological report form may help to homogenise PMF diagnosis. A close collaboration between the pathologist and the haematologist is desirable according to our survey.