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Background: Liposclerosing myxofibrous primary bone tumor is a rare benign bone lesion that was characterized by complex mixture of various histological elements. Methods: We have studied the radiological, clinical and pathological features of nine patients with this disorder. Pain and limping were the main symptoms. Results: Radiographic images typically showed a geographic lytic lesion with thick sclerotic margin, reflecting a pattern of slow growth. Histological sections revealed a polymorphic neoplasia characterized by predominant proliferation of stellate and fusiform cells aimed the myxoid matrix. Conclusions: These features suggest that the lesion may represent a variant of fibrous dysplasia with a high risk of malignant transformation. [ABSTRACT FROM AUTHOR]

Although the relationship between hip arthroplasty and the development of sarcoma was first described in the literature about forty years ago, this association is extremely rare. In the present case report, we describe the association between orthopedic implants and soft tissue sarcoma in a 79-year-old man who underwent primary total hip arthroplasty (THA) for coxarthrosis 24 years ago. In the present case report, we describe the clinical evolution and the radiographic and histopathological findings of the lesion. In the intraoperative period of the second revision surgery, loosening of the acetabular and femoral components in association with extensive areas of necrosis and metallosis was evidenced. We performed debridement of the hip and right thigh region and removed the implants. Due to the extent of the lesion and to necrosis, it was not possible to perform a new joint reconstruction. The histopathological diagnosis of high-grade undifferentiated pleomorphic sarcoma associated with extensive areas of metallosis was confirmed in tissue adjacent to the implant. The patient developed pulmonary metastases and died 6 months after the diagnosis. Despite the rarity of this association, sarcomas should be considered in the differential diagnosis of aseptic loosening, especially in the presence of metallosis in the peri-implant tissue. To our knowledge, the 24-year latency period between primary THA and the establishment of a sarcoma diagnosis is one of the longest reported to date., Competing Interests: Conflito de Interesses Os autores declaram não haver conflito de interesses., (The Author(s). This is an open access article published by Thieme under the terms of the Creative Commons Attribution 4.0 International License, permitting copying and reproduction so long as the original work is given appropriate credit ( https://creativecommons.org/licenses/by/4.0/ ).)

Although osteosarcoma is a rare disease, with a global incidence rate estimated at 5.0/million/year, it is the most frequent primary bone sarcoma in children and adolescents. In translational research, the patient-derived xenograft (PDX) model is considered an authentic in vivo model for several types of cancer, as tumorgrafts faithfully retain the biological characteristics of the primary tumors. Our goal was to investigate the association between PDX formation and clinical findings of osteosarcoma patients and the ability of the model to preserve in immunocompromized mice the characteristics of the parental tumor. A fresh sample of the patient tumor obtained from a representative biopsy or from surgical resection was implanted into nude mice. When tumor outgrowths reached ~1,500mm³, fresh PDX fragments were re-transplanted into new hosts. Engraftment in mice was obtained after a latency period of 19-225 days (median 92 days) in 40.54% of the implanted samples. We confirmed the histopathological fidelity between the patient tumor and their respective established PDXs, including the expression of biomarkers. PDX take rate was higher in surgical resection samples, in post-chemotherapy surgical samples and in samples from patients with metastatic disease at presentation. In conclusion, we have shown that the osteosarcoma PDX model reliably recapitulates the morphological aspects of the human disease after serial passage in mice. The observation that more aggressive forms of osteosarcoma, including those with metastatic disease at presentation, have a higher efficiency to generate PDXs provides a promising scenario to address several unanswered issues in clinical oncology.