Biopsy diagnosis of myeloproliferative neoplasms

Myeloproliferative neoplasms (MPN) are neoplastic diseases of haemopoiesis characterised by progressive development from initial phase to full blown stage up to final terminal phase with myelofibrosis or blastic transformation. Development of MPN is accompanied by subsequent changes in clinical and laboratory manifestation, as well as bone marrow (BM) morphology. In the last 15 years MPN categories are defined by universally accepted and widely used World Health Organisation (WHO) classification with complex diagnostic approach based on correlation of clinical and laboratory dates with morphology of neoplastic cells and results of molecular and genetic analyses. For the diagnosis of chronic myelogenous leukaemia the proof od BCR-ABL1 fusion gene remains crucial. The group of BCR-ABL1-negative MPN is defined by combination of "major" and "minor" WHO diagnostic criteria, stressing the importance of BM biopsy and recently identified MPN specific genetic abnormalities (predominantly the calreticuline gene mutations). This improves the differential diagnostic reliability, mainly in early MPN stages (essential throbocytemia, "prefibrotic" primary myelofibrosis and "prepolycythemic" polycythemia vera) showing similar clinical manifestions, as well as the possibility to separate MPN from non-neoplastic (reactive) changes of haemopoiesis. BM morphology can be affected by numerous external and internal pathologic impacts (especially MPN cytoreductive therapy, associated diseases and their treatment), what has to be respected by pathologist´s BM biopsy evaluation. The knowledge of relevant clinical information and basic laboratory dates, including results of molecular and genetic investigations is essential for reliable BM biopsy assessment of MPN patients. (author)