Diagnosis and quantification of bone marrow fibrosis are significantly biased by the pre-staining processing of bone marrow biopsies

Problems and pitfalls in grading of bone marrow fibrosis, collagen deposition and osteosclerosis - a consensus-based study

AIMS

In the era of potentially disease-modifying agents such as Janus kinase inhibitors, accurate grading and differentiation of bone marrow (BM) fibrosis has become more relevant to assess staging of disease and therapeutic effects. However, different fibrosis grading models have been used in the past without uniformity, including the proposal by the World Health Organization. Current scoring systems are based only on reticulin fibrosis. Therefore, additional assessment of collagen and the grade of osteosclerosis appear to be essential to discriminate all components of the complex BM fibrous matrix.

METHODS AND RESULTS

We evaluated problems and pitfalls regarding staining techniques and the interpretation of reticulin fibrosis on a total of 352 samples. Furthermore, we propose a minor modification of the current grading and separate scoring for collagen deposition and osteosclerosis. Reproducibility of gradings was tested among 11 haematopathologists in a blinded assessment. Overall, the inter-rater reliability of all three grading systems ranged between 0.898 and 0.926.

CONCLUSIONS

A standardized assessment of BM fibrosis with differentiation between reticulin, collagen and osteosclerosis is recommended to evaluate the various components of the fibrous matrix which may be delinked after therapy. In this regard, quality of staining and application of laboratory standards enable a highly reproducible scoring.

Aberrant proplatelet formation in chronic myeloproliferative neoplasms

Proplatelets represent pseudopodia of megakaryocytes which extend into bone marrow sinuses to release platelets. Proplatelets were visualized by immunohistochemical and confocal microscopy. In trephines from essential thrombocythaemia (ET, n=10), fibrotic (n=10) and pre-fibrotic (n=10) primary myelofibrosis (PMF) there was a significant increase of proplatelet density compared with normal bone marrow samples (n=10; p<0.001). Manifest fibrosis exhibited the highest density and volume ratio with significant differences to non-fibrotic PMF (p<0.001) and ET (p<0.001). This study demonstrates that besides megakaryocytic proliferation extensive pseudopodial proplatelet formation provides a hallmark of MPN. Fibrosing differ from non-fibrosing MPN by density and size of aberrant proplatelets.

Bone marrow aspirate and biopsy: a pathologist's perspective. II. interpretation of the bone marrow aspirate and biopsy

Bone marrow examination has become increasingly important for the diagnosis and treatment of hematologic and other illnesses. Morphologic evaluation of the bone marrow aspirate and biopsy has recently been supplemented by increasingly sophisticated ancillary assays, including immunocytochemistry, cytogenetic analysis, flow cytometry, and molecular assays. With our rapidly expanding knowledge of the clinical and biologic diversity of leukemia and other hematologic neoplasms, and an increasing variety of therapeutic options, the bone marrow examination has became more critical for therapeutic monitoring and planning optimal therapy. Sensitive molecular techniques, in vitro drug sensitivity testing, and a number of other special assays are available to provide valuable data to assist these endeavors. Fortunately, improvements in bone marrow aspirate and needle technology has made the procurement of adequate specimens more reliable and efficient, while the use of conscious sedation has improved patient comfort. The procurement of bone marrow specimens was reviewed in the first part of this series. This paper specifically addresses the diagnostic interpretation of bone marrow specimens and the use of ancillary techniques.

Marrow fibrosis predicts early fatal marrow failure in patients with myelodysplastic syndromes

Marrow fibrosis (MF) has rarely been studied in myelodysplastic syndromes (MDS). There are no data on occurrence and significance of MF in the context of the World Health Organization (WHO) classification of disease. In total, 349 bone marrow biopsies from 200 patients with primary MDS were examined for MF and its prognostic relevance. MF correlated with multilineage dysplasia, more severe thrombopenia, higher probability of a clonal karyotype abnormality, and higher percentages of blasts in the peripheral blood (P<0.002). Its frequency varied markedly between different MDS types ranging from 0 (RARS) to 16% (RCMD, RAEB, P<0.007). Two patients with MF showed a Janus kinase-2 mutation (V617F). Patients with MF suffered from marrow failure significantly earlier with shortening of the survival time down to 0.5 (RAEB-1/-2), and 1-2 (RCMD, RA) years in median (P<0.00005). The prognostic relevance of MF was independent of the International Prognostic Scoring System and the classification of disease.

CONCLUSION

The risk of MF Differs markedly between various subtypes of MDS. MF indicates an aggressive course with a significantly faster progression to fatal marrow failure and should therefore be considered in diagnosis, prognosis and treatment of disease.

Marrow fibrosis and its relevance during imatinib treatment of chronic myeloid leukemia

In chronic myeloid leukemia (CML), imatinib may reverse bone marrow fibrosis (MF). Whether the unfavorable prognosis of MF is also reversed and whether imatinib guarantees against evolution of MF are unclear as yet. Fifty-nine patients with Ph+ CML treated with > or = 400 mg imatinib/day were examined for MF in 6- to 12-month intervals. Imatinib effectively reversed initial MF (P<0.0005). However, during a follow-up period of up to 4.8 years, small foci with abnormal fiber increase (FFI) emerged in 8 of 30 pretreated and 6 of 29 non-pretreated patients. Patients with FFI showed a significantly lower probability of achieving a complete cytogenetic or major molecular response (36 versus 81%; P<0.007). During the further follow up, 57% of patients with FFI but none of the other patients suffered from full-blown MF (P=0.00005). None of the patients with FFI or MF showed a Janus kinase-2 mutation (V617F). Evolutions of FFI and MF were independent significant predictors of imatinib failure (P=0.0031), accelerated phase and death of patients (P=0.0001; multivariate analyses). Imatinib effectively reverses initial MF in CML, but neither eliminates its unfavorable prognosis nor guarantees completely against new evolution of MF.

Automated method to measure trabecular thickness from microcomputed tomographic scans and its application

Trabeculae form the internal bony mesh work and provide strength to the bone; interconnectivity, overall density, and trabecular thickness are important measures of the integrity of the internal architecture. Such strength is achieved only gradually during ontogeny, whereby an increase in trabecular thickness precedes an increase in mineralization. Loss of bone mass later in life may be compensated for by thickening of the remaining trabeculae. These facts, and the role of trabeculae in mineral homeostasis, highlight the importance of investigating trabecular thickness within and between species. While nondestructive imaging techniques (i.e., muCT and MRI) are becoming increasingly popular, quantification of trabecular thickness using nondestructive techniques has proved difficult owing to limitations imposed by scanning parameters, uniform thresholding, and partial volume averaging. Here we present a computer application, which aims to overcome these problems. Validation is carried out against a phantom and against trabecular thickness measured in corresponding histological sections. Good agreement was found between these measurements. Furthermore, when trabecular thickness is recorded for modern human fetal ilia, a trend toward trabecular thickness increase is found and is in line with reports of ontogenetic morphometric changes using histological sections. However, there are discrepancies. These may in part be due to partial volume effects of obliquely oriented structures. More crucial, however, are problems inherent in histological sections, e.g., shrinkage and distortion, especially where differences in mineralization are concerned; this may affect biological interpretations.