Micro-CT, Mechanical, and Histological Examination of the Effect of Local Adjuvants on Porcine Cortical Bone Following Intralesional Curettage of Bone Tumors.

BACKGROUND AND OBJECTIVES: Curettage is the removal of a tumor from the bone while preserving the surrounding healthy cortical bone, and is associated with higher rates of local recurrence. To lower these rates, curettage should be combined with local adjuvants, although their use is associated with damage to nearby healthy bone. OBJECTIVE: The purpose of this analysis is to determine the effect of local adjuvants on cortical porcine bone by using micro-computed tomography (micro-CT) along with histological and mechanical examination. METHODS: Local adjuvants were applied to porcine specimens under defined conditions. To assess changes in bone mineral density (BMD), a micro-CT scan was used. The pixel gray values of the volume of interest (VOI) were evaluated per specimen and converted to BMD values. The Vickers hardness test was employed to assess bone hardness (HV). The depth of necrosis was measured histologically using hematoxylin and eosin-stained tissue sections. RESULTS: A noticeable change in BMD was observed on the argon beam coagulation (ABC) sample. Comparable hardness values were measured on samples following electrocautery and ABC, and lowering of bone hardness was obtained in the case of liquid nitrogen. Extensive induced depth of necrosis was registered in the specimen treated with liquid nitrogen. CONCLUSION: This study determined the effect of local adjuvants on cortical bone by using micro-CT along with histological and mechanical examination. Phenolization and liquid nitrogen application caused a decrease in bone hardness. The bone density was affected in the range of single-digit percentage values. Liquid nitrogen induced extensive depth of necrosis with a wide variance of values.

Bone lesions - diagnostic approach using immunohistochemistry and molecular pathology.

Immunohistochemistry and molecular pathology play an essential role in the diagnosis of some focal bone lesions. These techniques may greatly help to distinguish primary bone tumors from metastatic diseases and allow a biologically important refinements in subclassification of round cell sarcomas. Recently, the diagnostic accuracy of organ and tumor specific antibodies has improved significantly. Knowledge of new type of antibodies and their meaningful use enables an accurate classification of the most undifferentiated carcinomas of unknown primary. However, the interpretation of immunohistochemical stains and molecular genetic analysis can be difficult in bone biopsies due to previous decalcification. This article summarizes the most important algorithmic approach to the diagnosis of bone tumors. It outlines the most frequently used tissue-specific antibodies. New advances in the understanding of bone tumorigenesis are also discussed.

Hyalinizing trabecular tumor of the thyroid gland with transcapsular invasion: a case report.

Hyalinizing trabecular tumor is a rare neoplasm usually with benign clinical behavior. Exceptionally it shows characteristic features of malignant tumors, such as the presence of venous or capsular invasion or distant metastasis. We report the case of 45-years-old female with a palpable nodule in the right lobe of the thyroid gland, 8x8x10 mm in size, well circumscribed, white colored. Histologically it was an encapsulated follicular neoplasm that consisted of medium to large-sized spindle-like to polygonal cells with elongated to round-shaped nuclei and small prominent nucleoli, sporadically with nuclear grooving and intranuclear pseudoinclusions, growing in alveolar to trabecular pattern. The tumor cells showed a distinctive membranous positivity for Ki-67. The tumor was surrounded by a thin fibrous capsule with multifocal transcapsular invasion. Keywords: hylinizing trabecular tumor - transcapsular invasion - thyroid gland - Ki-67.

Intraoperative diagnosis of the head and neck lesions, thyroid and parathyroid gland, bone and soft tissue, and genitourinary tract.

In this article, indications and pitfalls in frozen section diagnosis in selected organs and systems are discussed. The main indications for frozen section examination of head and neck and genitourinary system lesions are to evaluate the resection margin and the metastatic involvement of lymph nodes. Recently, intraoperative consultation has been introduced for identification of patients who might benefit from testis-sparing surgery. Preoperative fine-needle aspiration has greatly diminished the need for frozen section evaluation of thyroid lesions. The only reasonable indication for intraoperative examination of the thyroid is a lesion suspected of malignancy for which preoperative cytology is not aviable for various reasons. In contrast, frozen section is still routinely requested at many institutions to confirm the presence of parathyroid lesions, although precise differentiation between parathyroid hyperplasia, adenoma, and carcinoma is not possible in most cases by histological assesment alone. Tumors of bone and soft tissue are relatively rare, and most pathologists are unfamiliar with intraoperative consultation of these lesions. However, in many cases, limb-sparing management of bone and soft tissue sarcomas is dependent on intraoperative histological diagnosis. Accurate diagnosis is possible in most instances by correlating the histology with clinical and radiological data. In selected cases, histochemistry and/or intraoperative immunohistochemistry may be helpful in diagnosis of bone lesions.  Keywords: frozen section - head and neck - thyroid gland - parathyroid gland - soft tissue - urogenital tract.

Intravascular fasciitis leading to an aortic dissection. A case report.

Here we report on the case of a 61-year-old female with an accidental finding of intravascular fasciitis (IVF) affecting the ascending aorta in a specimen resected due to an acute aortic dissection. No infiltrative process of the aorta or surrounding soft tissues was grossly apparent. Microscopically, the lesion had poorly defined margins and was composed of plump spindle- and oval-shaped cells set in an abundant myxoid stroma. Immunohistochemically, cytoplasmic positivity for ß-catenin was observed and about 25% of cells were positive for calponin. The Ki-67 index was approximately 25% (increasing to about 50% in hot spot areas). Occasional isolated cells also showed positivity for alpha actin. Other markers were all negative in the tumor cells including; smooth muscle actin, desmin, h-caldesmon, D2-40, DOG1, S100 protein, CD34, CD31, ERG, melan A, HMB45, IgG, IgG4, ALK, cytokeratin AE1/AE3, and LCA. Intravascular fasciitis is a benign myofibroblastic proliferation which most commonly occurs in subcutaneous tissues and may mimic malignancy. To the best of our knowledge this is only the 2nd ever reported case of IVF affecting the aorta. Keywords: intravascular fasciitis - nodular fasciitis - soft tissue lesions - myofibroblasts - aorta.

Soft tissue metastasis of mediastinal non-functioning paraganglioma with unusual TTF-1 expression: a potential diagnostic pitfall.

Metastatic extra-adrenal paragangliomas are very rare and can represent diagnostic challenges. We report a case of 69-year-old man with a tumor of the right shoulder. Histologic and immunohistochemical examinations confirmed the diagnosis of paraganglioma. Surprisingly, tumor cells were diffusely thyroid transcription factor 1 (TTF-1) positive. Succinate dehydrogenase complex subunit B (SDHB) deficiency has not been detected. Inherited syndromes associated with paragangliomas were ruled out. The primary tumor was identified in the mediastinum. This is the first report of TTF-1 expression in paraganglioma. To avoid misdiagnosis, careful clinical and pathological examination of any tumor with organoid growths pattern is necessary.

[Giant cell-rich lesions of bone and their differential diagnosis]. / Obrovskobunecné léze kostí a jejich diferenciální diagnostika.

Giant cell-rich lesions form a heterogeneous group of reactive and truly neoplastic processes with diverse clinical presentation and biological behavior. Common to all of them are variably numerous multinucleated osteoclast-like giant cells and the presence of mononuclear stroma. Based on the histological picture alone it is sometimes impossible to reliably distinguish certain tumors from each other. The pathologist has to know the patient´s age, the exact localization, tumor growth dynamics and its radiographic characteristics. Secondary reactive changes occur frequently and these can completely alter the morphology of the lesion and thus overshadow the underlying neoplasm. Reparative changes in a pathological fracture may histologically mimic primary bone malignancy. Immunohistochemistry helps only in select cases and molecular genetic methods still have very limited utility for the diagnosis of giant cell-rich tumors. It is necessary to correlate the microscopic features of the lesion with clinical and radiological findings. A correct diagnosis is of paramount importance for proper treatment and prognosis.

Cancer stem cell markers in pediatric sarcomas: Sox2 is associated with tumorigenicity in immunodeficient mice.

The three most frequent pediatric sarcomas, i.e., Ewing's sarcoma, osteosarcoma, and rhabdomyosarcoma, were examined in this study: three cell lines derived from three primary tumor samples were analyzed from each of these tumor types. Detailed comparative analysis of the expression of three putative cancer stem cell markers related to sarcomas-ABCG2, CD133, and nestin-was performed on both primary tumor tissues and corresponding cell lines. The obtained results showed that the frequency of ABCG2-positive and CD133-positive cells was predominantly increased in the respective cell lines but that the high levels of nestin expression were reduced in both osteosarcomas and rhabdomyosarcomas under in vitro conditions. These findings suggest the selection advantage of cells expressing ABCG2 or CD133, but the functional tests in NOD/SCID gamma mice did not confirm the tumorigenic potential of cells harboring this phenotype. Subsequent analysis of the expression of common stem cell markers revealed an evident relationship between the expression of the transcription factor Sox2 and the tumorigenicity of the cell lines in immunodeficient mice: the Sox2 levels were highest in the two cell lines that were demonstrated as tumorigenic. Furthermore, Sox2-positive cells were found in the respective primary tumors and all xenograft tumors showed apparent accumulation of these cells. All of these findings support our conclusion that regardless of the expression of ABCG2, CD133 and nestin, only cells displaying increased Sox2 expression are directly involved in tumor initiation and growth; therefore, these cells fit the definition of the cancer stem cell phenotype.

[WHO classification of tumours of soft tissue and bone 2013: the main changes compared to the 3rd edition]. / WHO klasifikace nádoru mekkých tkání a kostí 2013: hlavní zmeny oproti 3. vydání

In early 2013, the new classification of tumours of soft tissue and bones was released. This edition belongs to the fourth series of so-called Blue Books published under the auspices of the World Health Organisation (WHO). The current classification follows the previous third edition, from which it differs in several aspects. The vast majority of changes are related to the soft tissue tumour section, which was enriched with three new chapters, some entities or terms were removed, new diagnoses were introduced, and several tumours were reallocated to other categories. Albeit to a lesser extent, similar changes have occurred also in the classification of bone tumours. Compared to the previous edition, more detailed molecular and cytogenetic data were incorporated in the current issue. The rapidly increasing knowledge of the genetics of mesenchymal tumours allows us to make more accurate diagnoses as well as to better understand of the pathogenesis of these lesions. However, abundant molecular and cytogenetic data highlight an increasing problem of growing numbers of genetic overlaps even among quite different tumours. The coexistence of several grading systems of soft tissue tumours is another controversial issue mentioned in the recent WHO classification. The main advantages and limitations of the two most widely used grading systems are also discussed.

Clear surgical margins as a prognostic indicator for disease recurrence, with no impact on survival rates in patients with myxofibrosarcoma.

Myxofibrosarcoma presents an infiltrating growth pattern that results in a high tendency for local recurrence. Clear margin resection is challenging because of microscopic infiltration. The purpose of the present study was to analyze the overall and disease-free survival rates of patients with myxofibrosarcoma and the prognostic factors that determine both survival and disease recurrence. Among the 111 patients included in our study, the 5-year overall survival rate was 65.5%. An age of more than 65 years (hazard ratio [HR] 1.9 [95% confidence interval (CI) 1.4-5.6]; p < 0.001), a tumor size of more than 5 cm (HR 2.8 [95% CI 0.9-8.1]; p = 0.049) and the G3 tumor grade (HR 14.1 [95% CI 2.1-105.0]; p < 0.001) negatively affected overall survival. The 5-year recurrence-free survival rate was 49.4%. R1/R2-type resection (HR 2.4 [95% CI 1.0-5.6]; p = 0.048) had a detrimental effect on tumor recurrence. Clear margins had a positive impact on recurrence-free survival, but did not significantly affect overall patient survival, suggesting that other factors may play a more significant role in determining patient outcomes. A surgical margin of 2 mm was not sufficient to significantly influence the incidence of recurrence. Consequently, a wider surgical margin may be necessary to reduce the risk of myxofibrosarcoma recurrence.

Phenotype and oxidative burst of low-density neutrophil subpopulations are altered in common variable immunodeficiency patients.

Common variable immunodeficiency disorder (CVID) is the most common form of primary antibody immunodeficiency. Due to low antibody levels, CVID patients receive intravenous or subcutaneous immunoglobulin replacement therapy as treatment. CVID is associated with the chronic activation of granulocytes, including an increased percentage of low-density neutrophils (LDNs). In this study, we examined changes in the percentage of LDNs and the expression of their surface markers in 25 patients with CVID and 27 healthy donors (HD) after in vitro stimulation of whole blood using IVIg. An oxidative burst assay was used to assess the functionality of LDNs. CVID patients had increased both relative and absolute LDN counts with a higher proportion of mLDNs compared to iLDNs, distinguished based on the expression of CD10 and CD16. Immature LDNs in the CVID and HD groups had significantly reduced oxidative burst capacity compared to mature LDNs. Interestingly we observed reduced oxidative burst capacity, reduced expression of CD10 after stimulation of WB, and higher expression of PD-L1 in mature LDNs in CVID patients compared to HD cells. Our data indicate that that the functional characteristics of LDNs are closely linked to their developmental stage. The observed reduction in oxidative burst capacity in mLDNs in CVID patients could contribute to an increased susceptibility to recurrent bacterial infections among CVID patients.

Hand2 Immunohistochemistry in the Diagnosis of Paragangliomas and Other Neuroendocrine Neoplasms.

Hand2 is a core transcription factor responsible for chromaffin cell differentiation. However, its potential utility in surgical pathology has not been studied. Thus, we aimed to investigate its expression in paragangliomas, other neuroendocrine neoplasms (NENs), and additional non-neuroendocrine tumors. We calibrated Hand2 immunohistochemistry on adrenal medulla cells and analyzed H-scores in 46 paragangliomas (PGs), 9 metastatic PGs, 21 cauda equina neuroendocrine tumors (CENETs), 48 neuroendocrine carcinomas (NECs), 8 olfactory neuroblastomas (ONBs), 110 well-differentiated NETs (WDNETs), 10 adrenal cortical carcinomas, 29 adrenal cortical adenomas, 8 melanomas, 41 different carcinomas, and 10 gastrointestinal stromal tumors (GISTs). Both tissue microarrays (TMAs) and whole sections (WSs) were studied. In 171 NENs, previously published data on Phox2B and GATA3 were correlated with Hand2. Hand2 was positive in 98.1% (54/55) PGs, but only rarely in WDNETs (9.6%, 10/104), CENETs (9.5%, 2/21), NECs (4.2%, 2/48), or ONBs (12.5%, 1/8). Any Hand2 positivity was 98.1% sensitive and 91.7% specific for the diagnosis of PG. The Hand2 H-score was significantly higher in primary PGs compared to Hand2-positive WDNETs (median 166.3 vs. 7.5; p < 0.0001). Metastatic PGs were positive in 88.9% (8/9). No Hand2 positivity was observed in any adrenal cortical neoplasm or other non-neuroendocrine tumors, with exception of 8/10 GISTs. Parasympathetic PGs showed a higher Hand2 H-score compared to sympathetic PGs (median H-scores 280 vs. 104, p < 0.0001). Hand2 positivity in NENs serves as a reliable marker of primary and metastatic PG, since other NENs only rarely exhibit limited Hand2 positivity.

Proximal Tibia Tumour Location and Curettage Are Major Risk Factors of Local Recurrence in Giant Cell Tumour of Bone.

Giant cell tumour of bone (GCTB) is one of the most common local aggressive tumourous lesions with a wide variety of biological behaviour. However, there are no clear indicative criteria when choosing the type of procedure and the complication rates remain high, especially in terms of local recurrence. The purpose of the study was to (1) identify the main risk factors for local recurrence, (2) evaluate the recurrence-free survival in dependence on neoadjuvant denosumab use and the type of procedure, and (3) compare the functional outcomes after curettage and en bloc resection. The group included 102 patients with GCTB treated between 2006 and 2020. The mean age of patients was 34.4 years (15-79). The follow-up period was 8.32 years (2-16) on average. Local recurrence occurred in 14 patients (29.8%) who underwent curettage and in 5 patients (10.6%) after en bloc resection. Curettage was shown to be a factor in increasing recurrence rates (OR = 3.64 [95% CI: 1.19-11.15]; p = 0.023). Tibial location was an independent risk factor for local recurrence regardless of the type of surgery (OR = 3.22 [95% CI: 1.09-9.48]; p = 0.026). The recurrence-free survival rate of patients treated with resection and denosumab was higher compared to other treatments at five years postoperatively (p = 0.0307). Functional ability and pain as reported by patients at the latest follow-up were superior after curettage compared to resection for upper and lower extremity (mean difference: -4.00 [95% CI: -6.81 to -1.18]; p < 0.001 and mean difference: -5.36 [95% CI: -3.74 to -6.97]; p < 0.001, respectively). Proximal tibia tumour location and curettage were shown to be major risk factors for local recurrence in GCTB regardless of neoadjuvant denosumab treatment. The recurrence-free survival rate of patients treated with resection and denosumab was higher compared to other treatments. The functional outcome of patients after curettage was better compared to en bloc resection.

Soft tissue sarcoma with ZC3H7B::BCOR fusion in a male mimicking low-grade fibromyxoid sarcoma - A case report.

Diagnosis of soft tissue tumors is often challenging, given the large number of entities, often with non-specific or overlapping morphology. Although morphology still plays an important part in diagnostic process, additional studies including immunohistochemistry and molecular genetics are often needed to arrive at correct diagnosis. We report a case of 61-year-old male with subcutaneous tumor in right hip area, that was surgically removed. The tumor was composed of uniform bland spindle cells in mild to moderately cellular myxoid nodules, with limited areas of collagenization and the diagnosis of low grade fibromyxoid sarcoma was made. The tumor recurred 3 years after the initial diagnosis and the new sample showed a high-grade round cell sarcoma with limited residual low-grade areas and non-specific immunoprofile after extended immunohistochemical work-up. Molecular analysis demonstrated ZC3H7B::BCOR fusion. Sarcomas with ZC3H7B::BCOR fusion occurring outside of uterus are exceedingly rare. A comprehensive review of previously published cases and a short discussion about classification of the entity is provided, together with data about morphology and immunoprofile of the lesions. The case also underscores the necessity of extended work up of soft tissue tumors with unusual immunohistochemical or morphological features in order to accurately assess their biological potential.

Outcomes of Intercalary Endoprostheses as a Treatment for Metastases in the Femoral and Humeral Diaphysis.

BACKGROUND: The purpose of this study was to evaluate the implant survival, functional score and complications of intercalary endoprostheses implanted for metastatic involvement of the femoral and humeral diaphysis. METHODS: The selected group covered patients with bone metastasis who were surgically treated with an intercalary endoprosthesis between 2012 and 2021. The functional outcome was evaluated with the Musculoskeletal Tumor Society (MSTS) scoring system, and complications were evaluated by using the failure classification for prosthetics designed by Henderson. RESULTS: The mean follow-up was 29.8 months. In our group of 25 patients with 27 intercalary endoprostheses (18 femurs, 9 humeri), there were 7 implant-related complications (25.9%), which were more common on the humerus (4 cases, 44.4%) than on the femur (3 cases, 16.7%). Only type II failure-aseptic loosening (5 cases, 18.5%)-and type III failure-structural failure (2 cases, 7.4%)-occurred. There was a significantly higher risk of aseptic loosening of the endoprosthesis in the humerus compared with that in the femur (odds ratio 13.79, 95% confidence interval 1.22-151.05, p = 0.0297). The overall cumulative implant survival was 92% 1 year after surgery and 72% 5 years after surgery. The average MSTS score was 82%. The MSTS score was significantly lower (p = 0.008) in the humerus (75.9%) than in the femur (84.8%). CONCLUSIONS: The resection of bone metastases and replacement with intercalary endoprosthesis has excellent immediate functional results with an acceptable level of complications in prognostically favourable patients.

Transcription factor c-Myb: novel prognostic factor in osteosarcoma.

The transcription factor c-Myb is an oncoprotein promoting cell proliferation and survival when aberrantly activated/expressed, thus contributing to malignant transformation. Overexpression of c-Myb has been found in leukemias, breast, colon and adenoid cystic carcinoma. Recent studies revealed its expression also in osteosarcoma cell lines and suggested its functional importance during bone development. However, the relevance of c-Myb in control of osteosarcoma progression remains unknown. A retrospective clinical study was carried out to assess a relationship between c-Myb expression in archival osteosarcoma tissues and prognosis in a cohort of high-grade osteosarcoma patients. In addition, MYB was depleted in metastatic osteosarcoma cell lines SAOS-2 LM5 and 143B and their growth, chemosensitivity, migration and metastatic activity were determined. Immunohistochemical analysis revealed that high c-Myb expression was significantly associated with poor overall survival in the cohort and metastatic progression in young patients. Increased level of c-Myb was detected in metastatic osteosarcoma cell lines and its depletion suppressed their growth, colony-forming capacity, migration and chemoresistance in vitro in a cell line-dependent manner. MYB knock-out resulted in reduced metastatic activity of both SAOS-2 LM5 and 143B cell lines in immunodeficient mice. Transcriptomic analysis revealed the c-Myb-driven functional programs enriched for genes involved in the regulation of cell growth, stress response, cell adhesion and cell differentiation/morphogenesis. Wnt signaling pathway was identified as c-Myb target in osteosarcoma cells. Taken together, we identified c-Myb as a negative prognostic factor in osteosarcoma and showed its involvement in the regulation of osteosarcoma cell growth, chemosensitivity, migration and metastatic activity.

Low-level copy number changes of MYC genes have a prognostic impact in medulloblastoma.

High-level amplifications of MYC genes are associated with poor outcomes in childhood medulloblastoma (MB). However, the occurrence of MYCN and MYCC copy number increases below the intense amplification pattern is rarely reported, and its clinical impact has not yet been determined. Here, we describe this phenomenon and its prognostic significance in a cohort of 29 MB patients. Using interphase fluorescence in situ hybridization (I-FISH), low-level copy number alterations, i.e. gain of MYCN, were shown in 5/27 (19%) samples, whereas amplification was revealed in only 1/27 (4%) samples. MYCC gain was revealed in 6/29 (21%) MB, while amplification was disclosed in only 2/29 (7%). Hyperploidy and co-incidence of gains in both MYC loci were frequently observed in samples with copy number aberrations. Survival analysis has clearly shown that MYC copy number increases are associated with lowered event-free survival and overall survival in MB. In the case of MYCN, this negative correlation was statistically significant. We conclude that limited numerical alterations in loci 2p24 (MYCN) and 8q24 (MYCC), as assessed by I-FISH, are present in MB with a higher frequency than high-level amplifications. Poor prognoses were observed in patients with copy number increases in MYC genes. Our data illustrate the importance of further investigations in multicenter trials to better refine the emerging genomic-based prognostic stratification in MB.

New Target for Precision Medicine Treatment of Giant-Cell Tumor of Bone: Sunitinib Is Effective in the Treatment of Neoplastic Stromal Cells with Activated PDGFRß Signaling.

Giant-cell tumor of bone (GCTB) is an intermediate type of primary bone tumor characterized by locally aggressive growth with metastatic potential. The aim of this study was to identify new druggable targets among the cell signaling molecules involved in GCTB tumorigenesis. Profiles of activated signaling proteins in fresh-frozen tumor samples and tumor-derived cell lines were determined using phosphoprotein arrays. Analysis of the obtained data revealed epidermal growth factor receptor (EGFR) and platelet-derived growth factor receptor beta (PDGFRß) as potential targets, but only the PDGFR inhibitor sunitinib caused a considerable decrease in stromal cell viability in vitro. Furthermore, in the case of a 17-year-old patient suffering from GCTB, we showed that the addition of sunitinib to the standard treatment of GCTB with the monoclonal antibody denosumab resulted in the complete depletion of multinucleated giant cells and mononuclear stromal cells in the tumor tissue. To summarize, the obtained data showed that a specific receptor tyrosine kinase (RTK) signaling pattern is activated in GCTB cells and plays an important role in the regulation of cell proliferation. Thus, activated RTKs and their downstream signaling pathways represent useful targets for precision treatment with low-molecular-weight inhibitors or with other types of modern biological therapy.

Improved osteosarcoma survival with addition of mifamurtide to conventional chemotherapy - Observational prospective single institution analysis.

PURPOSE: Conventional osteosarcoma is an orphan disease. Current treatment approaches include combining a three drug chemotherapy schedule and surgery. The 3- and 5-year event-free survival (EFS) in localized disease is roughly 65 and 60%, respectively. The registration study of mifamurtide reported survival benefit, but some methodological controversies have been insufficient for FDA market authorization in contrast to EMA. METHODS: prospective single centre survival analysis of a mifamurtide addition to conventional therapy in 23 patients over a 5.5 year enrolment period is reported and compared to a historical control of 26 patient with localized disease. Bias arising from observational methodology was addressed using Landmark analysis and time-dependent Cox models. Blood count dynamics were analysed during the treatment. RESULTS: The adverse event profile was as expected with no dose limiting toxicities. There were no local relapses observed, one patient died in the first complete remission due to doxorubicin cardiotoxicity, one patient had pulmonary metastatic relapse. The observed 3- and 5-year EFS was 87.4% (CI 72.4-100%) and 87.4% (CI 72.4-100%), progression free survival (PFS) was 92.9% (CI 80.3-100%) and 92.9% (CI 80.3-100%), overall survival was 94.1% (CI 83.6-100) and 80.7% (CI 58.3-100), respectively. Comparison to the historical control showed statistically significant better PFS for mifamurtide patients (Landmark analysis; p = 0.044). Risk of progression was 5-times lower for the mifamurtide group (Cox model; HR 0.21, p = 0.136). Only subtle differences in lymphocyte counts were observed across treatment. CONCLUSION: the PFS benefit of mifamurtide is reported herein. The addition of mifamurtide could be considered as a best treatment option for localized osteosarcoma.