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Tumor cells can migrate from a primary cancer and form metastases by localizing to niches within other organs including the bone marrow, where tumor cells may exploit the hematopoietic stem cell niche. The precise composition of the premetastatic and the hematopoietic niches and the degree of overlap between them remain elusive. Because the extracellular matrix protein fibronectin is expressed in the pre-metastatic lung microenvironment, we evaluated the implications of its loss, as well as those of loss of its primary receptor subunit, β1 integrin, in various bone marrow cell types both in breast cancer bone metastasis and hematopoiesis. Using eight transgenic mouse models, we established that fibronectin production by osterix-expressing marrow cells, or β1 integrin expression (on vav, mx, or leptin receptor expressing cells), affects MDA-MB-231 breast cancer cell numbers in the bone marrow. Additionally, we identified stromal subpopulations that modulate transmigration through blood vessel walls. Not the number of tumor cells, but rather the changes in the microenvironment dictated whether the tumor progresses. Furthermore, hematopoiesis, particularly myelopoiesis, was affected in some of the models showing changes in tumor homing. In conclusion, there is partial overlap between the pre-metastatic and the hematopoietic niches in the bone marrow. Moreover, we have delineated a cascade starting with fibronectin secreted by pre-osteoblastic cells, which potentially acts on β1 integrin in specific stromal cell subsets, thereby inhibiting the formation of new breast cancer lesions in the bone marrow. This work therefore sheds light on the role of various stromal cell subpopulations that influence tumor behavior and affect hematopoiesis., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024. Published by Elsevier Inc.)

Metastasis is the major cause of cancer-related deaths. Neuroblastoma (NB), a childhood tumor has been molecularly defined at the primary cancer site, however, the bone marrow (BM) as the metastatic niche of NB is poorly characterized. Here we perform single-cell transcriptomic and epigenomic profiling of BM aspirates from 11 subjects spanning three major NB subtypes and compare these to five age-matched and metastasis-free BM, followed by in-depth single cell analyses of tissue diversity and cell-cell interactions, as well as functional validation. We show that cellular plasticity of NB tumor cells is conserved upon metastasis and tumor cell type composition is NB subtype-dependent. NB cells signal to the BM microenvironment, rewiring via macrophage mgration inhibitory factor and midkine signaling specifically monocytes, which exhibit M1 and M2 features, are marked by activation of pro- and anti-inflammatory programs, and express tumor-promoting factors, reminiscent of tumor-associated macrophages. The interactions and pathways characterized in our study provide the basis for therapeutic approaches that target tumor-to-microenvironment interactions., (© 2023. The Author(s).)

Nestin is an intermediate filament protein, which was originally detected in neuroepithelial stem cells. Besides its use as a phenotypic marker of mesenchymal stem cells in the hematopoeitic stem cell niche, the functional interpretation of nestin + cells remains elusive. We investigated the cellular expression of nestin in bone marrow trephine biopsies of MPN patients, following myeloablation at a stage of hypocellularity during early regeneration. Here, nestin is highly expressed in mature osteocytes, arteriolar endothelial and perivascular cells and small capillaries within the bone marrow space, but not in sinusoid lining cells. This is in stark contrast to nestin expression pattern in myeloproliferative neoplasms that show hypercellularity due to oncogenic driver mutations. Here, nestin is expressed exclusively in endothelial cells of arterioles, but not in osteocytes or small capillaries. Thus, the pattern of nestin expression following myeloablation inversely correlates with cellularity in the bone marrow. This nestin expression pattern is mimicking early postnatal transcriptional programming during bone marrow development. We show that nestin expression in osteocytes occurs across different species following transplant and also in bone marrow metastasis., (© 2022 The Authors. British Journal of Haematology published by British Society for Haematology and John Wiley & Sons Ltd.)

Toll-like receptors (TLRs) are a family of transmembrane receptors whose signaling control cellular processes of cell proliferation, survival, apoptosis, angiogenesis, remodeling, and repair of tissues. Polymorphisms in TLR genes can change the balance between pro and anti-inflammatory cytokines, modulating the risk of infection, chronic inflammation, and cancer. Although many studies have demonstrated the direct involvement of TLR signaling in the benefit of tumor cells in certain cancers, little is known about the influence of these gene polymorphisms on myeloproliferative neoplasms (MPNs). In this context, the objective of the study was to investigate a possible association between the TLR polymorphisms and the development of MPNs. 167 patients diagnosed with MPN and 222 healthy controls from the same region were evaluated. Genomic DNA was extracted and the TLR2 (rs5743708), TLR4 (rs4986790, rs4986791), TLR9 (rs5743836, rs187084) and JAK2V617F polymorphisms were genotyped by PCR-RFLP. The statistical analysis was performed by OpenEpi and SNPstat software. The JAK2V617F mutation was found in 68.32% of patients. TLR9-1486C/T CT genotype was less frequent in patients with polycythemia vera (PV) (OR 0.39, 95% CI 0.20-0.78, P = 0.025). When haplotype frequencies were analyzed, -1237T/-1486C (TLR9) was also less frequent in men (OR 0.58, 95% CI 0.36-0.94) and JAK negative men patients (OR 0.43, 95% CI 0.21-0.88). We can infer that the TLR9-1486 CT genotype could be associated with protection for PV and the TLR9-1237T/-1486C haplotype, protection for men, as well as for JAK negative men patients with MPN. There were no associations between TLR2 and TLR4 gene polymorphisms and MPN., (© 2021. The Author(s), under exclusive licence to Springer Nature B.V.)

One of the greatest barriers to curative treatment of neuroblastoma is its frequent metastatic outgrowth prior to diagnosis, especially in cases driven by amplification of the MYCN oncogene. However, only a limited number of regulatory proteins that contribute to this complex MYCN -mediated process have been elucidated. Here we show that the growth arrest-specific 7 ( GAS7 ) gene, located at chromosome band 17p13.1, is preferentially deleted in high-risk MYCN-driven neuroblastoma. GAS7 expression was also suppressed in MYCN -amplified neuroblastoma lacking 17p deletion. GAS7 deficiency led to accelerated metastasis in both zebrafish and mammalian models of neuroblastoma with overexpression or amplification of MYCN . Analysis of expression profiles and the ultrastructure of zebrafish neuroblastoma tumors with MYCN overexpression identified that GAS7 deficiency led to (i) downregulation of genes involved in cell-cell interaction, (ii) loss of contact among tumor cells as critical determinants of accelerated metastasis, and (iii) increased levels of MYCN protein. These results provide the first genetic evidence that GAS7 depletion is a critical early step in the cascade of events culminating in neuroblastoma metastasis in the context of MYCN overexpression. SIGNIFICANCE: Heterozygous deletion or MYCN -mediated repression of GAS7 in neuroblastoma releases an important brake on tumor cell dispersion and migration to distant sites, providing a novel mechanism underlying tumor metastasis in MYCN-driven neuroblastoma. See related commentary by Menard, p. 2815 ., (©2021 American Association for Cancer Research.)

Background: Long-term outcome remains poor for children with high-risk neuroblastoma (five-year overall survival [OS] ∼50%). Our objectives were to (a) identify prognostic biomarkers and apply them in a nomogram to identify the subgroup of ultra-high-risk patients at highest risk of disease progression/death, for whom novel frontline therapy is urgently needed; and (b) validate the nomogram in an independent cohort., Methods: A total of 1820 high-risk patients (≥18 months old with metastatic neuroblastoma), diagnosed 1998-2015, from the International Neuroblastoma Risk Groups (INRG) Data Commons were analyzed in a retrospective cohort study. Using multivariable Cox regression of OS from diagnosis, a nomogram was created from prognostic biomarkers to predict three-year OS. External validation was performed using the SIOPEN HR-NBL1 trial cohort (n = 521), evidenced by receiver operating characteristic curves., Results: The nomogram, including MYCN status (P < 0.0001), lactate dehydrogenase (LDH) (P = 0.0007), and presence of bone marrow metastases (P = 0.004), had robust performance and was validated. Applying the nomogram at diagnosis (a) gives prognosis of an individual patient and (b) identifies patients predicted to have poor outcome (three-year OS was 30% ± 5% for patients with a nomogram score of > 82 points; 58% ± 1% for those ≤82 points). Median follow-up time was 5.5 years (range, 0-14.1)., Conclusions: In high-risk neuroblastoma, a novel, publicly available nomogram using prognostic biomarkers (MYCN status, LDH, presence of bone marrow metastases; https://neuroblastoma.shinyapps.io/High-Risk-Neuroblastoma-Nomogram/) has the flexibility to apply a clinically suitable and context-specific cutoff to identify patients at highest risk of death. This will facilitate testing urgently needed new frontline treatment options to improve outcome for these children., (© 2020 Wiley Periodicals LLC.)

Emerging evidence has indicated that long non‑coding RNAs (lncRNAs) are closely associated with the pathogenesis of ischemic stroke. It has been reported that small nucleolar RNA host gene 12 (SNHG12) serves a critical role in ischemic stroke by acting as a competitive endogenous RNA (ceRNA). SNHG12 competes with various microRNAs (miRs) to regulate RNA transcription of specific targets. However, the effect of SNHG12 on oxygen‑glucose deprivation (OGD)‑induced neuronal apoptosis has rarely been reported. The present study demonstrated that SNHG12 expression was downregulated in OGD‑injured SH‑SY5Y cells. Furthermore, miR‑181a‑5p was reported as a target of SNHG12 and was negatively regulated by SNHG12. Moreover, NEGR1 was a target of miR‑181a‑5p, which functions as a negative regulator of NEGR1 in OGD‑induced neuronal apoptosis. In summary, the results strongly confirmed the hypothesis that SNHG12 functions as a ceRNA for miR‑181a‑5p and regulates the expression of NEGR1 thus inhibiting OGD‑induced apoptosis of SH‑SY5Y cells. Neuronal apoptosis aggravates brain damage during ischemic stroke, indicating that the activation of SNHG12 and NEGR1 expression and inhibition of miR‑181a‑5p may be a novel strategy for the clinical treatment of ischemic stroke.

Introduction: In the context of neuroblastoma (NB), the screening for bone marrow (BM) metastasis is a recurrent issue for hematology laboratory routine practice. Detection of low tumor burden using light microscopy is often difficult. In this regard, our objective was to evaluate the performance of multiparametric flow cytometry (FC) for detecting NB metastatic cells in BM., Methods: We applied a new FC multiparametric panel allowing the analysis of the co-expression of 5 surface markers: GD2 (disialoganglioside 2), CD9, CD56, CD81, and CD90, on CD45-negative BM cell populations, and compared results with BM biopsy immunohistochemistry, which is the reference method., Results: In spike-in tests, the multiparametric FC successfully detected NB cells mixed in peripheral blood mononuclear cells to a level of 0.01%. FC analysis was performed on 45 sets of BM aspirates sampled from 21 children, either at diagnosis or during follow-up. Combining multiparametric FC with light microscopy improved NB metastasis detection, with a higher sensitivity (76.9% vs 61.5%) and a higher specificity (94.4% vs 77.8%) as compared to light microscopy alone. At the time of diagnosis, multiparametric FC detected NB metastatic cells in all cases., Conclusion: These results illustrate the performance of multiparametric FC analysis to detect metastatic BM infiltration of NB. This is of particular interest in an emergency context, since when combined with light microscopy, it enhances the detection of metastatic invasion within a short timeframe, allowing an adapted and rapid clinical management., (© 2019 John Wiley & Sons Ltd.)

Background: While colorectal cancer (CRC) patients with localized disease have a favorable prognosis, the five-year-survival rate in patients with distant spread is still below 15%. Hence, a detailed understanding of the mechanisms regulating metastasis formation is essential to develop therapeutic strategies targeting metastasized CRC. The notch pathway has been shown to be involved in the metastatic spread of various tumor entities; however, the impact of its target gene HEYL remains unclear so far., Methods: In this study, we functionally assessed the association between high HEYL expression and metastasis formation in human CRC. Therefore, we lentivirally overexpressed HEYL in two human patient-derived CRC cultures differing in their spontaneous metastasizing capacity and analyzed metastasis formation as well as tumor cell dissemination into the bone marrow after xenotransplantation into NOD.Cg-Prkdc scid Il2rg tm1Wjl /SzJ (NSG) mice., Results: HEYL overexpression decreased tumor cell dissemination and the absolute numbers of formed metastases in a sub-renal capsular spontaneous metastasis formation model, addressing all steps of the metastatic cascade. In contrast, metastatic capacity was not decreased following intrasplenic xenotransplantation where the cells are placed directly into the blood circulation., Conclusion: These results suggest that HEYL negatively regulates metastasis formation in vivo presumably by inhibiting intravasation of metastasis-initiating cells.

Ruxolitinib is an FDA approved janus kinase (JAK)1/2 inhibitor used to treat myeloproliferative neoplasms (MPNs), including myelofibrosis and polycythemia vera. We aimed to determine the metabolic consequences of ruxolitinib treatment in patients with MPNs. We performed a retrospective single-center cohort study utilizing an electronic medical record based database of patients who began treatment with ruxolitinib for MPNs from January 2010 to March 2017. We also examined the effects of ruxolitinib on adipose tissue JAK/STAT signaling in a mouse model. 127 patients were identified, of which 69 had data available for weight, and at least one other parameter of interest before, and 72 weeks after starting ruxolitinib. Mean baseline weight was 73.9 ± 17.0 kg, and 78.54 ± 19.1 kg at 72 weeks (p < 0.001). 50% of patients gained >5% body weight. Baseline body mass index (BMI) was 25.8 ± 4.8 kg/m 2 , and 27.5 ± 5.5 kg/m 2 at 72 weeks (p < 0.001). Patients treated with ruxolitinib had a higher systolic blood pressure, serum AST, and ALT at 72 weeks, compared with baseline (p = 0.03, p = 0.01, p = 0.04, respectively). In mice, ruxolitinib decreased basal and GH-stimulated STAT5 phosphorylation in adipose tissue. As pharmacological JAK1/2 inhibitors are being developed and used in clinical practice, it is important to understand their long-term metabolic consequences.

Auer rod-like inclusions are rarely seen in B-cell neoplasms patients. Here, we present a case of B-cell lymphoma with Auer rod-like inclusions in lymphoma cells. By light and transmission electron microscopy, these structures closely resembled Auer rods which were found in acute myeloid leukemia. The Auer rod-like inclusions were negative for cytochemical staining of MPO, α-naphthyl acetate esterase, and periodic acid-Schiff. Immunostaining and flow cytometric analysis confirmed monoclonal Kappa-positive malignant lymphocytes. Interestingly, the Auer rod-like inclusions exhibited diverse ultrastructural features, which ranged from fusiform, to needle-shape, to round, to crystalline cuboid, to long rod, to short rod and others; some were membrane structures, some membrane-free dense structures, and some lamellar structures. The patient was diagnosed with B-cell lymphoma with bone marrow infiltration., (Copyright © 2019. Published by Elsevier Inc.)

Introduction: We describe peripheral blood smear, bone marrow morphology, histopathology, immunohistochemistry, including BRAF V600E, and molecular testing results of patients with metastatic melanoma to the bone marrow., Methods: We performed a retrospective review for patients with metastatic melanoma to the bone marrow at our institution. Bone marrow morphology, histology, immunophenotyping, and cytogenetic/molecular genetic testing were reviewed, and BRAF V600E immunohistochemistry was performed. Results were compared to the literature., Results: We identified four patients with metastatic melanoma to the bone marrow presenting with at least one cytopenia. Two of the four patients had leukoerythroblastosis, with three patients having atypical cells on bone marrow aspirate/touch preparation, and all patients had aggregates of atypical cells on biopsy. Immunohistochemistry for S100, Melan A, and HMB45 confirmed the diagnosis in all patients, and BRAF V600E immunohistochemistry was detected in two of four patients, which correlated with molecular testing findings. Review of the literature found 27 total patients, with normocytic anemia and leukoerythroblastosis as common peripheral blood smear findings., Conclusions: Features including cytopenias (typically anemia), leukoerythroblastosis, and morphology of cohesive, large atypical cells in aspirate and biopsy, and immunohistochemical expression for S100, Melan A, and HMB45 were present in patients with metastatic melanoma. BRAF V600E immunohistochemistry is useful as a surrogate marker of molecular results. Regardless of clinical history, at the time of the bone marrow biopsies, hematologic malignancies are in the main differential diagnosis and very rarely included metastatic melanoma, likely due to the under-recognized metastatic potential of melanoma to the bone marrow., (© 2019 John Wiley & Sons Ltd.)

Background: The aim of this study was to assess the utility of F-fluoro-2-deoxy-D-glucose (F-FDG) positron emission tomography/computed tomography (PET/CT) in assessing bone marrow involvement (BMI) compared with bone marrow biopsy (BMB) in the initial staging of pediatric patients with non-Hodgkin lymphoma (NHL), Hodgkin lymphoma (HL), Ewing sarcoma (ES), and neuroblastoma (NB)., Procedure: A total of 94 patients (57 boys, 37 girls, median age 7 y, range 1 to 18 y) with newly diagnosed NHL, HL, ES, and NB between July 2014 and December 2017, who underwent BMB and F-FDG PET/CT before chemotherapy were included in this study. There were 36 patients with NHL, 27 HL, 16 ES, and 15 NB. F-FDG PET/CT and BMB results were reviewed and compared retrospectively., Findings: Retrospective analysis of data from 94 pediatric patients (57 boys, 37 girls, median age 7 y, range 1 to 18 y) was performed. Of the 94 patients, 29 had BMI on F-FDG PET/CT. BMB was positive in 14, negative in 13, and insufficient in 2 of these 29 patients. In 65 patients negative on F-FDG PET/CT, BMB was also negative in 54 and insufficient in 7. For the whole group, sensitivity, specificity, and positive and negative predictive values of F-FDG PET/CT in detecting bone marrow metastasis at the time of diagnosis were 90.6%, 100%, 100%, and 95.4% and those of BMB were 53.1%, 87.1%, 94.4%, and 80.6%, respectively., Conclusion: Our study demonstrates that F-FDG PET/CT predicts BMI better than BMB. F-FDG PET/CT may be used at initial staging of pediatric patients with NHL, HL, ES, and NB.

Cancer is a major cause of death in children worldwide, with B-lineage cell acute lymphoblastic leukemia (B-ALL) being the most frequent childhood malignancy. Relapse, treatment failure and organ infiltration worsen the prognosis, warranting a better understanding of the implicated mechanisms. Cortactin is an actin-binding protein involved in cell adhesion and migration that is overexpressed in many solid tumors and in adult B-cell chronic lymphocytic leukemia. Here, we investigated cortactin expression and potential impact on infiltration and disease prognosis in childhood B-ALL. B-ALL cell lines and precursor cells from bone marrow (BM) and cerebrospinal fluid (CSF) of B-ALL patients indeed overexpressed cortactin. In CXCL12-induced transendothelial migration assays, transmigrated B-ALL cells had highest cortactin expression. In xenotransplantation models, only cortactin high -leukemic cells infiltrated lungs, brain, and testis; and they colonized more easily hypoxic BM organoids. Importantly, cortactin-depleted B-ALL cells were significantly less efficient in transendothelial migration, organ infiltration and BM colonization. Clinical data highlighted a significant correlation between high cortactin levels and BM relapse in drug-resistant high-risk B-ALL patients. Our results emphasize the importance of cortactin in B-ALL organ infiltration and BM relapse and its potential as diagnostic tool to identify high-risk patients and optimize their treatments.

The bone marrow is a preferential site for both reactive and neoplastic histiocytic proliferations. The differential diagnosis ranges from reactive histiocyte hyperplasia in systemic infections, vaccinations, storage diseases, post myeloablative therapy, due to increased cell turnover, and in hemophagocytic lymphohistiocytosis, through extranodal Rosai-Dorfman disease to neoplasms derived from histiocytes, including histiocytic sarcomas (HS), Langerhans cell histiocytoses (LCH), Erdheim-Chester disease (ECD), and disseminated juvenile xanthogranuloma (JXG). One of the most important recent developments in understanding the biology of histiocytic neoplasms and in contributing to diagnosis was the detection of recurrent mutations of genes of the Ras/Raf/MEK/ERK signaling pathway, in particular the BRAF V600E mutation, in LCH and ECD. Here, we summarize clinical and pathological findings of 17 histiocytic neoplasms that were presented during the bone marrow symposium and workshop of the 18th European Association for Haematopathology (EAHP) meeting held in Basel, Switzerland, in 2016. A substantial proportion of these histiocytic neoplasms was combined with clonally related lymphoid (n = 2) or myeloid diseases (n = 5, all ECD). Based on the latter observation, we suggest excluding co-existent myeloid neoplasms at initial staging of elderly ECD patients. The recurrent nature of Ras/Raf/MEK/ERK signaling pathway mutations in histiocytic neoplasms was confirmed in 6 of the 17 workshop cases, illustrating their diagnostic significance and suggesting apotential target for tailored treatments.

Neuroblastoma (NB) is the most common extracranial pediatric solid tumor. Around 70% of patients with metastatic disease at diagnosis present bone-marrow infiltration, which is considered a marker of poor outcome; however, the mechanism underlying this specific tropism has to be elucidated. Tumor-derived exosomes may support metastatic progression in several tumors by interacting with the microenvironment, and may serve as tumor biomarkers. The main objective of this study is to identify an exosomal signature associated with NB metastatic bone-marrow dissemination. Therefore, the proteomic cargo of exosomes isolated from NB cell lines derived from primary tumor and bone-marrow metastasis is characterized. The comparison among exosomal proteins show 15 proteins exclusively present in primary tumor-derived exosomes, mainly involved in neuronal development, and 6 proteins in metastasis-derived exosomes related to cancer progression. Significant proteins obtain with statistical analysis performed between the two groups, reveal that primary tumor exosomes contain a higher level of proteins involved in extra-cellular matrix (ECM) assembly and adhesion, as well as in neuronal development. Exosomes isolated from bone-marrow metastasis exhibit proteins involved in ameboidal cell migration and mitochondrial activity. This work suggests that proteomic profiling of NB-derived exosomes reflects the tumor stage and may be considered as potential tumor biomarker., (© 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Background: This study evaluated the relationship between 18 F-fluorodeoxyglucose (FDG) uptake in bone marrow (BM) on positron emission tomography (PET)/computed tomography (CT) imaging and serum inflammatory markers and assessed the prognostic value of FDG uptake of BM in patients with non-small-cell lung cancer (NSCLC) who underwent curative surgical resection., Patients and Methods: We retrospectively enrolled 110 NSCLC patients who underwent FDG PET/CT imaging and subsequent curative surgical resection. The maximum standardized uptake value of NSCLC (Tmax), mean FDG uptake of BM (BM SUV), and BM to liver uptake ratio (BLR) were measured. The relationships between BM SUV, BLR, and serum inflammatory markers were evaluated and the prognostic significance of PET/CT parameters for predicting recurrence-free survival (RFS) and overall survival (OS) were assessed., Results: BM SUV and BLR were significantly associated with serum C-reactive protein (CRP) level, white blood cell count, and the neutrophil to lymphocyte ratio (NLR). BLR was also significantly correlated with serum albumin and the platelet to lymphocyte ratio. In univariate analysis, tumor, node, metastases (TNM) stage, serum CRP level, NLR, Tmax, and BLR were significant prognostic factors for RFS and OS, whereas histopathology and tumor size were significant prognostic factors for RFS. In multivariate analysis, BLR, histopathology, TNM stage, and Tmax were independent prognostic factors for RFS and TNM stage and Tmax were independent prognostic factors for OS., Conclusion: FDG uptake of BM on PET/CT imaging was correlated with serum inflammatory markers and was an independent predictor for RFS, along with FDG uptake of NSCLC., (Copyright © 2016 Elsevier Inc. All rights reserved.)

Objective: The study evaluated the significance of 18F fluorodeoxyglucose ( 18 F-FDG) uptake of bone marrow (BM) for predicting progression-free survival (PFS) in lymphoma patients without BM involvement., Subjects and Methods: Ninety-five patients with histopathologically proven lymphoma, 7 Hodgkin's lymphoma and 88 non-Hodgkin's lymphoma, who underwent 18 F-FDG positron emission tomography/computed tomography (PET/CT) and BM biopsy for staging work-up and 40 normal subjects were retrospectively enrolled. Maximal 18 F-FDG uptake of lymphoma (Lmax), mean 18 F-FDG uptake of BM (BM SUV) and BM-to-liver uptake ratio (BLR) were measured. Prognostic value of BM SUV and BLR for predicting PFS were assessed., Results: Of the 95 patients, 35 (36.8%) were histopathologically or clinically diagnosed with BM involvement of lymphoma. There were significant differences of BLR among lymphoma patients with/without BM involvement and normal subjects (P<0.05). For all patients, high risk indicated by International Prognostic Index (IPI) score and Lmax were significantly associated with PFS on multivariate analysis (P<0.05). For 60 patients without BM involvement, BM SUV and BLR were independent prognostic factors for PFS along with performance status and Lmax (p<0.05). Among patients without BM involvement, high 18 F-FDG uptake of BM was associated with significantly worse PFS than low 18 F-FDG uptake of BM, with no significant difference in PFS apparent compared to patients with BM involvement., Conclusion: In lymphoma patients without BM involvement, 18 F-FDG uptake of BM was significantly associated with worse PFS. Patients with high 18 F-FDG uptake of BM showed similar prognosis to those with BM involvement.

Background: Loss of disialoganglioside 2 (GD2) expression in neuroblastoma (NB) bone marrow cells has been reported in rare cases. This study investigated prospectively the frequency and the patterns of visible GD2 loss at diagnosis, during treatment, and at recurrence., Methods: Bone marrow aspirates of patients with new or recurrent stage 4 and 4S NB diagnosed between January 1, 2002 and August 31, 2013 were investigated in parallel by cytology and GD2 immunocytology. Complete negative immunostaining was defined if staining was absent in all and partial if absent in a portion and/or in case of atypical faint staining., Results: Of 1,261 investigated trial patients of all stages, 474 had unequivocal cytological bone marrow infiltration at initial diagnosis. Thirty-seven patients had tumor cells with complete or partial negative GD2 staining at initial diagnosis, nine during chemotherapy, and 11 at recurrence (altogether 12.0%). The percentage of GD2 negativity in stages 4 and 4S were similar (13% and 9%, respectively). Complete negativity was seen in 14 and partial in 43 cases. Twenty-one cases changed from positive to negative (15 to partial and six to complete) and three cases from negative to positive staining (two to partial and one to complete). The GD2 negative and positive groups were not different regarding tumor sites, molecular characteristics, histology, and tumor markers. Children with stage 4 and GD2 negativity tended to be older at diagnosis (42 vs. 32 months, P = 0.056). Event-free survival and overall survival comparing negative versus positive staining did not show any differences., Conclusions: Complete or partial lack of GD2 staining on NB cells in bone marrow is more frequent than currently recognized., (© 2016 Wiley Periodicals, Inc.)

Despite all the knowledge, the cellular and molecular mechanisms involved in myeloproliferative neoplasm (MPN) pathophysiology remain unclear. Authors have shown galectin-1 (Gal-1) and 3 playing roles in tumour angiogenesis and fibrosis, which were correlated with poor prognosis in patients with MPN. In the present study LGALS1 and LGALS3 were differently expressed between polycythemia vera, essential thrombocythemia (ET) and primary myelofibrosis (PMF) diseases. Increased LGALS3 expression was associated with a negative JAK2 V617F status mutation in leucocytes from PMF but not in patients with ET without this mutation. However, a positive Janus kinase 2 (JAK2) V617F cell line established from patients with ET (SET-2 cells) when treated with JAK inhibitor presented high levels of LGALS3. Additionally, high LGALS1 expression was found in CD34(+) cells but not in leucocytes from patients with PMF, in absence of JAK2 V617F mutation, and also in SET-2 cells treated with JAK inhibitor. Thus, our findings indicate that differential expression of LGALS1 and/or LGALS3 in patients with MPN is linked with JAK2 V617F status mutation in these diseases and state of cell differentiation., (Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://www.bmj.com/company/products-services/rights-and-licensing/)

Despite the success in detecting breast cancer (BC) early and, with aggressive therapeutic intervention, BC remains a clinical problem. The bone marrow (BM) is a favorable metastatic site for breast cancer cells (BCCs). In BM, the survival of BCCs is partly achieved by the supporting microenvironment, including the presence of immune suppressive cells such as mesenchymal stem cells (MSCs). The heterogeneity of BCCs brings up the question of how each subset interacts with the BM microenvironment. The cancer stem cells (CSCs) survive in the BM as cycling quiescence cells and, forming gap junctional intercellular communication (GJIC) with the hematopoietic supporting stromal cells and MSCs. This type of communication has been identified close to the endosteum. Additionally, dormancy can occur by soluble mediators such as cytokines and also by the exchange of exosomes. These latter mechanisms are reviewed in the context of metastasis of BC to the BM for transition as dormant cells. The article also discusses how immune cells such as macrophages and regulatory T-cells facilitate BC dormancy. The challenges of studying BC dormancy in 2-dimensional (2-D) system are also incorporated by proposing 3-D system by engineering methods to recapitulate the BM microenvironment., (Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.)

Background: Disseminated tumor cells (DTC) in the bone marrow (BM) of primary breast cancer (BC) patients are a promising surrogate marker of micrometastatic spread and an independent predictor of poor prognosis for disease-free survival (DFS) and overall survival (OS). The present study aims to analyze DTCs as an independent prognostic factor for DFS/OS in tumor biology and bisphosphonate treatment., Methods: A total of 504 patients with operable primary BC and a median observation time of 72.3 months [lower quartile (LQ) 58.1; upper quartile (UQ) 82.8] have been included. DTCs were detected via immunohistochemistry as MUC-1 positive cells in the BM of 59.13 % (298 of 504) of the patients. The immunophenotyping of cancer cells was achieved immunohistochemically as well., Results: For luminal A/B carcinoma patients, we observed a significant benefit of BM DTC negativity with respect to DFS (luminal A, P = 0.0498; luminal B, P = 0.0224). In triple-negative patients, DTC-negative BM was associated with a longer OS (P = 0.0326). In a multivariate Cox survival analysis relating to DFS and OS, the DTC status was identified as an independent prognostic factor for DFS in luminal A/B BC (P = 0.0071). A multivariate Cox survival analysis among DTC-positive patients with luminal immunophenotype showed bisphosphonate application (P = 0.0326) to be an independent prognostic factor for DFS., Conclusions: The findings of our multivariate analyses reveal BM DTC positivity as an independent risk factor for DFS particularly in luminal A/B BC patients. This might be a novel criterion for the identification of candidates most likely to benefit from additional adjuvant therapy possibly including bisphosphonates.

Background: Micrometastases in bone marrow of women with early breast cancer were first identified immunocytochemically in the 1980s. We report on the original cohort of women with a median follow-up of 30 years., Patients and Methods: In total, 350 women with primary breast cancer had eight bone marrow aspirates examined with antibody to epithelial membrane antigen. Data on long-term mortality were obtained via record linkage to death certification., Results: At a 30-year median follow-up, 79 out of 89 (89%) patients with micrometastases have died compared with 202 out of 261 (77%) without (hazard ratio=1.46 (95% CI 1.12-1.90), P=0.0043). Most marked effect of micrometastases on overall survival (OS) was seen in patients aged ⩽ 50 at surgery (N=97, P=0.012), and on all patients within 10 years of diagnosis. In multivariable analyses, the presence of micrometastases was no longer a statistically significant prognostic factor., Conclusions: Bone marrow micrometastases are predictive for OS, particularly in the first decade and in younger patients.

Disseminated carcinomatosis of the bone marrow is characterized by widespread bone metastasis (bone marrow infiltration) from solid tumors with hematological disorders coexisted. This disease is frequently complicated with gastric cancer among solid tumors although its incidence is very rare. In recent years, technological innovations in diagnosis and treatment for cancer have remarkably improved, which made survival rates of various cancers prolonged. Prognosis of disseminated carcinomatosis of the bone marrow associated with gastric cancer, however, is still poor (less than a year), possibly because this disease has not been given attention due to low incidence. In this review, I summarize the results obtained for the past, and propose ways to improve the prognosis of this disease.

The study of breast cancer dormancy in the bone marrow is an exceptionally difficult undertaking due to the complexity of the interactions of dormant cells with their microenvironment, their rarity and the overwhelming excess of hematopoietic cells. Towards this end, we developed an in vitro 2D clonogenic model of dormancy of estrogen-sensitive breast cancer cells in the bone marrow. The model consists of a few key elements necessary for dormancy. These include 1) the use of estrogen sensitive breast cancer cells, which are the type likely to remain dormant for extended periods, 2) incubation of cells at clonogenic density, where the structural interaction of each cell is primarily with the substratum, 3) fibronectin, a key structural element of the marrow and 4) FGF-2, a growth factor abundantly synthesized by bone marrow stromal cells and heavily deposited in the extracellular matrix. Cells incubated with FGF-2 form dormant clones after 6 days, which consist of 12 or less cells that have a distinct flat appearance, are significantly larger and more spread out than growing cells and have large cytoplasm to nucleus ratios. In contrast, cells incubated without FGF-2 form primarily growing colonies consisting of>30 relatively small cells. Perturbations of the system with antibodies, inhibitors, peptides or nucleic acids on day 3 after incubation can significantly affect various phenotypic and molecular aspects of the dormant cells at 6 days and can be used to assess the roles of membrane-localized or intracellular molecules, factors or signaling pathways on the dormant state or survival of dormant cells. While recognizing the in vitro nature of the assay, it can function as a highly useful tool to glean significant information about the molecular mechanisms necessary for establishment and survival of dormant cells. This data can be used to generate hypotheses to be tested in vivo models.

Context: Neuroblastoma (NB) is the most common extracranial tumor of childhood. Although most cases have a distinctive histology, a subset of primitive cases require immunohistochemical studies to distinguish them from other small round blue cell tumors of childhood. Immunohistochemistry is also used to detect small amounts of tumor metastatic to the bone marrow and in posttreatment samples with obscuring fibrosis, calcification, or inflammation. The transcription factor PHOX2B is essential for the differentiation and survival of sympathetic neurons and chromaffin cells, and therefore is highly specific for the peripheral autonomic nervous system., Objective: To determine the diagnostic utility of PHOX2B immunohistochemistry as a marker of primary, treated, and metastatic NB., Design: Neuroblastoma tissue microarrays were stained with PHOX2B, CD57, and synaptophysin. Arrays containing rhabdomyosarcoma, Ewing sarcoma, and Wilms tumor were stained with PHOX2B, and negative bone marrow samples were stained with PHOX2B and CD57., Results: PHOX2B and CD57 were similar to synaptophysin in their ability to detect NB. PHOX2B and CD57 similarly showed robust staining in posttreatment NB and NB metastatic to the bone marrow. In contrast to the cytoplasmic staining pattern seen with synaptophysin and CD57, clear and strong nuclear PHOX2B permitted identification of individual tumor cells. PHOX2B staining was absent in all cases of rhabdomyosarcoma, Ewing sarcoma, and Wilms tumor, and in the negative bone marrow., Conclusions: PHOX2B and CD57 are useful markers of NB. PHOX2B is specific for NB in its differential diagnosis with other small round cell tumors, and its nuclear staining may be helpful for accurate bone marrow tumor quantification.

The acquired somatic JAK2-V617F mutation is present in >80% of patients with myeloproliferative neoplasms (MPNs). Stat3 plays a role in hematopoietic homeostasis and might influence the JAK2-V617F-driven MPN phenotype. We crossed our transgenic SclCre;V617F mice with a conditional Stat3 knockout strain and performed bone marrow transplantations into lethally irradiated recipient mice. The deletion of Stat3 increased the platelet numbers in SclCre;V617F;Stat3(fl/fl) mice compared with SclCre;V617F;Stat3(fl/+) or SclCre;V617F;Stat3(+/+) mice. Stat3 deletion also normalized JAK2-V617F-induced neutrophilia. Megakaryocyte progenitors were elevated, especially in the spleen, and a slight increase in myelofibrosis was noted. We observed increased mRNA expression levels of Stat1 and Stat1 target genes and augmented phosphorylation of Stat1 protein in bone marrow and spleen of JAK2-V617F mice after Stat3 deletion. The survival of Stat3-deficient mice expressing JAK2-V617F was reduced. Inflammatory bowel disease, previously associated with shortened survival of Stat3-deficient mice, was less prominent in the bone marrow transplantation setting, possibly by limiting deletion of Stat3 to hematopoietic tissues only. In conclusion, deletion of Stat3 in hematopoietic cells from JAK2-V617F mice did not ameliorate the course of MPN, but rather enhanced thrombocytosis and shortened the overall survival., (© 2015 by The American Society of Hematology.)

Neuroblastoma is a childhood tumour with heterogeneous characteristics and children with metastatic disease often have a poor outcome. Here we describe the establishment of neuroblastoma patient-derived xenografts (PDXs) by orthotopic implantation of viably cryopreserved or fresh tumour explants of patients with high risk neuroblastoma into immunodeficient mice. In vivo tumour growth was monitored by magnetic resonance imaging and fluorodeoxyglucose-positron emission tomography. Neuroblastoma PDXs retained the undifferentiated histology and proliferative capacity of their corresponding patient tumours. The PDXs expressed neuroblastoma markers neural cell adhesion molecule, chromogranin A, synaptophysin and tyrosine hydroxylase. Whole genome genotyping array analyses demonstrated that PDXs retained patient-specific chromosomal aberrations such as MYCN amplification, deletion of 1p and gain of chromosome 17q. Thus, neuroblastoma PDXs recapitulate the hallmarks of high-risk neuroblastoma in patients. PDX-derived cells were cultured in serum-free medium where they formed free-floating neurospheres, expressed neuroblastoma gene markers MYCN, CHGA, TH, SYP and NPY, and retained tumour-initiating and metastatic capacity in vivo. PDXs showed much higher degree of infiltrative growth and distant metastasis as compared to neuroblastoma SK-N-BE(2)c cell line-derived orthotopic tumours. Importantly, the PDXs presented with bone marrow involvement, a clinical feature of aggressive neuroblastoma. Thus, neuroblastoma PDXs serve as clinically relevant models for studying and targeting high-risk metastatic neuroblastoma., (© 2014 The Authors. Published by Wiley Periodicals, Inc. on behalf of UICC.)

The clonal bone marrow stem cell disorders essential thrombocythemia (ET), polycythemia vera (PV) and primary myelofibrosis (PMF) belong to the group of Philadelphia chromosome negative myeloproliferative neoplasia (Ph- MPN). In 2005 the JAK2(V617F) mutation was discovered which has generated more insight in the pathogenetic mechanism of the MPNs. More mutations have been detected in MPN patients since. However, the underlying cause of MPN has not been discovered so far. The mechanism of increased angiogenesis in MPNs and the development of fibrosis in the bone marrow in PMF patients and in some ET and PV patients is still not known. This review will focus on the most important molecular pathogenetic mechanisms in MPN patients.

Fueled by the growing interest in stem cell biology and the promise of regenerative medicine, study of the hematopoietic stem cell (HSC) microenvironment has provided critical insights into normal and malignant hematopoiesis. Notch receptor signaling in this microenvironment is a critical regulator of HSC fate and differentiation. Notch signaling also has the potential to modulate the growth of various malignant cell types, as evidenced by the growing list of hematologic cancers and other malignancies associated with either mutations in Notch genes or alterations in Notch signaling. In both health and disease, activation of Notch signaling predominantly exerts influence through stromal cell interactions with the tumor or stem cell microenvironments. Definitive evidence from transgenic mouse models has shown that alterations in stromal cell signaling from the bone marrow niche can induce malignant outgrowth of preleukemic clones and leukemia. Understanding how Notch receptor signals in the bone marrow microenvironment govern stem cell behavior will advance our understanding of cancer pathogenesis in hematologic malignancies and may have implications for treating metastatic solid tumors involving bone. These microenvironmental interactions are potential therapeutic targets for treating and preventing a variety of diseases, including bone marrow failure disorders, myelodysplastic syndromes, leukemia, and lymphoma., (© 2014 New York Academy of Sciences.)

Background: Enzalutamide is a novel antiandrogen with proven efficacy in metastatic castration-resistant prostate cancer (mCRPC)., Objective: To evaluate enzalutamide's effects on cancer and on androgens in blood and bone marrow, and associate these with clinical observations., Design, Setting, and Participants: In this prospective phase 2 study, 60 patients with bone mCRPC received enzalutamide 160mg orally daily and had transilial bone marrow biopsies before treatment and at 8 wk of treatment., Outcome Measurements and Statistical Analysis: Androgen signaling components (androgen receptor [AR], AR splice variant 7 (ARV7), v-ets avian erythroblastosis virus E26 oncogene homolog [ERG], cytochrome P450, family 17, subfamily A, polypeptide 1 [CYP17]) and molecules implicated in mCRPC progression (phospho-Met, phospho-Src, glucocorticoid receptor, Ki67) were assessed by immunohistochemistry; testosterone, cortisol, and androstenedione concentrations were assessed by liquid chromatography-tandem mass spectrometry; AR copy number was assessed by real-time polymerase chain reaction. Descriptive statistics were applied., Results and Limitations: Median time to treatment discontinuation was 22 wk (95% confidence interval, 19.9-29.6). Twenty-two (37%) patients exhibited primary resistance to enzalutamide, discontinuing treatment within 4 mo. Maximal prostate-specific antigen (PSA) decline ≥ 50% and ≥ 90% occurred in 27 (45%) and 13 (22%) patients, respectively. Following 8 wk of treatment, bone marrow and circulating testosterone levels increased. Pretreatment tumor nuclear AR overexpression (> 75%) and CYP17 (> 10%) expression were associated with benefit (p = 0.018). AR subcellular localization shift from the nucleus was confirmed in eight paired samples (with PSA decline) of 23 evaluable paired samples. Presence of an ARV7 variant was associated with primary resistance to enzalutamide (p = 0.018). Limited patient numbers warrant further validation., Conclusions: The observed subcellular shift of AR from the nucleus and increased testosterone concentration provide the first evidence in humans that enzalutamide suppresses AR signaling while inducing an adaptive feedback. Persistent androgen signaling in mCRPC was predictive of benefit and ARV7 was associated with primary resistance., Patient Summary: We report a first bone biopsy study in metastatic prostate cancer in humans that searched for predictors of outcome of enzalutamide therapy. Benefit is linked to a pretreatment androgen-signaling signature., Trial Registration: ClinicalTrials.gov identifier NCT01091103., (Published by Elsevier B.V.)

Bone marrow (BM) metastasis remains one of the main causes of death associated with solid tumors as well as multiple myeloma (MM). Targeting the BM niche to prevent or modulate metastasis has not been successful to date. Here, we show that stromal cell-derived factor-1 (SDF-1/CXCL12) is highly expressed in active MM, as well as in BM sites of tumor metastasis and report on the discovery of the high-affinity anti-SDF-1 PEGylated mirror-image l-oligonucleotide (olaptesed-pegol). In vivo confocal imaging showed that SDF-1 levels are increased within MM cell-colonized BM areas. Using in vivo murine and xenograft mouse models, we document that in vivo SDF-1 neutralization within BM niches leads to a microenvironment that is less receptive for MM cells and reduces MM cell homing and growth, thereby inhibiting MM disease progression. Targeting of SDF-1 represents a valid strategy for preventing or disrupting colonization of the BM by MM cells., (Copyright © 2014 The Authors. Published by Elsevier Inc. All rights reserved.)

Disease-specific mutations facilitate diagnostic precision and drug target discovery. In myeloproliferative neoplasms (MPN), this is best exemplified by the chronic myeloid leukemia-associated BCR-ABL1. No other mutation in MPN has thus far shown a similar degree of diagnostic accuracy or therapeutic relevance. However, JAK2 and KIT mutations are detected in more than 90% of patients with polycythemia vera and systemic mastocytosis, respectively, and are therefore used as highly sensitive clonal markers in these diseases. JAK2 and MPL mutations also occur in essential thrombocythemia (ET) and primary myelofibrosis (PMF), but their diagnostic value is limited by suboptimal sensitivity and specificity. The molecular diagnostic gap in JAK2/MPL-unmutated ET/PMF is now partially addressed by the recent discovery of calreticulin (CALR) mutations in the majority of such cases. However, bone marrow morphology remains the central diagnostic platform and is essential for distinguishing ET from prefibrotic PMF and diagnosing patients those do not express JAK2, MPL or CALR (triple-negative). The year 2013 was also marked by the description of CSF3R mutations in the majority of patients with chronic neutrophilic leukemia (CNL). Herein, we argue for the inclusion of CALR and CSF3R mutations in the World Health Organization classification system for ET/PMF and CNL, respectively.

The interferon-γ (IFNγ)/signal transducer and activator of transcription 1 (Stat1) pathway shows higher activity in patients with essential thrombocythemia (ET) than in polycythemia vera (PV) and was proposed to be promoting the ET phenotype. We explored the phenotypic consequences of Stat1 deficiency on the effects of Janus kinase 2 (JAK2)-V617F in vivo by crossing mice expressing JAK2-V617F with Stat1 knockout mice. JAK2-V617F;Stat1(-/-) double transgenic mice showed higher red cell parameters and lower platelet counts compared with JAK2-V617F;Stat1(+/+) mice. Bone marrow transplantation reproduced these phenotypic changes in wild-type recipients, demonstrating that the effect of Stat1 is cell-intrinsic and does not require a Stat1-deficient microenvironment. Deletion of Stat1 increased burst-forming unit-erythroid and reduced colony-forming unit-megakaryocyte colony formation driven by JAK2-V617F, but was not sufficient to completely normalize the platelet count. Gata1, a key regulator of megakaryopoiesis and erythropoiesis, was decreased in Stat1-deficient platelets. V617F transgenic mice with thrombocytosis had higher serum levels of IFNγ than normal controls and patients with ET showed higher IFNγ serum levels than patients with PV. Together, these results support the concept that activating Stat1 in the presence of JAK2-V617F, for example, through IFNγ, constrains erythroid differentiation and promotes megakaryocytic development, resulting in ET phenotype., (© 2014 by The American Society of Hematology.)

Background: CXCR4 chemokine receptor is constitutively expressed on normal and malignant B lymphocytes derived from patients with B-cell lymphoproliferative disorders and has a significant role in cell migration to lymph nodes and bone marrow. Non-Hodgkin's lymphomas (NHL) constitute a heterogeneous group of lymphoproliferative diseases, which can localize not only to lymph nodes, but also can migrate to peripheral blood and metastase to other organs, including bone marrow., Aim: The purpose of this study was to determine CXCR4 gene expression in peripheral blood and bone marrow of NHL patients before and after treatment., Methods: Samples of lymphoma lymph nodes, peripheral blood and bone marrow aspirates of patients with B-cell NHL were taken at diagnosis and after chemotherapy. Gene expression was determined by the reverse transcription (RT)-polymerase chain reaction method. Expression was estimated from 0 AU (no amplificate signal) to 3 AU (maximal amplificate signal)., Results: No significant difference in the level of CXCR4 expression was found in reactive lymph nodes compared to lymphoma samples We observed high level of CXCR4 expression in most patients before treatment: in bone marrow: 3 AU-10 pts, 2 AU-8 pts, 1 AU-2 pts. In peripheral blood: 3 AU-14 pts, 2 AU-4 pts, 1 AU-1 pts, 0 AU-1 pts. After chemotherapy, significant decrease in CXCR4 expression was observed. Bone marrow: 3 AU-5 pts, 2 AU-7 pts, 1 AU-5 pts, 0 AU-3 pts (p = 0.03). Peripheral blood: 3 AU-2 pts, 2 AU-6 pts, 1 AU-10 pts, 0 AU-2 pts (p = 0.0002). There was a good response to treatment in patients with significant decrease of CXCR4 expression in the bone marrow after treatment with 10-fold lower risk of death (p = 0.03)., Conclusions: Decrease in CXCR4 expression in the bone marrow of NHL patients after chemotherapy may be a good prognostic factor.

A 69 years old woman with adult T-cell leukemia (ATL) (chronic type) was referred for a fluorine-18 fluorodeoxyglucose positron emission computed tomography ((18)F-FDG PET/CT). Multiple hypermetabolic pulmonary and bone lesions were evidence. The patient underwent chemotherapy, but did not respond, and she died approximately 8 months from the onset of symptoms. Autopsy showed ATL cells infiltrating the lung parenchyma and the pulmonary hilum. In conclusion, we present a case of hypermetabolic pulmonary lesions associated with thoracic CT findings on a (18)F-FDG PET/CT scan in a patient with a chronic adult T-cell leukemia.

Polyclonal mesenchymal cells (fibroblasts, endothelial cells, pericytes, osteoblasts, reticular cells, adipocytes, etc.) of the bone marrow create a functional microenvironment, which actively contributes to the maintenance of hemopoesis. This takes place through cellular interactions via growth factors, cytokines, adhesion molecules and extracellular matrix components, as well as through the control of calcium and oxygen concentration. Inflammatory and neoplastic diseases of the bone marrow result in pathologic interaction between hemopoietic progenitors and stromal cells. This may lead to the activation and expansion of the stroma and to the accumulation of reticulin and collagen fibers produced by mesenchymal cells. Clinically relevant fiber accumulation, termed as myelofibrosis accompanies many diseases, although, the extent and the consequence of myelofibrosis are variable in different disorders. The aim of this review is to summarize basic features of the normal bone marrow mesenchymal environment and the pathological process leading to myelofibrosis. In addition, the special features of myelofibrosis in bone marrow diseases, including myeloproliferative neoplasia, myelodysplastic syndrome and other neoplastic conditions are discussed.