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Objective: To depict histological and imaging features of myoepithelial carcinoma of the bone and soft tissue., Materials and Methods: We retrospectively examined histological features in 22 patients with myoepithelial carcinoma of the bone (4 patients) and soft tissue (18 patients) at a single institution. Imaging analysis of 15 patients (bone, 3 patients; soft tissue, 12 patients;) with preoperative images involved classifying lytic bone lesions via the modified Lodwick-Madewell classification; the growth patterns of soft tissue lesions were classified as well-defined, focally invasive, or diffusely invasive., Results: Local recurrence occurred in eight out of 22 patients (36.3%). Four of 22 patients (18.2%) had metastasis at presentation, whereas 11 of 22 patients (50.0%) had distant metastasis during follow-up. Severe cytological pleomorphism was observed in 14 of 22 patients (63.6%), and 10 of 22 tumors (45.5%) showed ≥ 10 mitoses/10 high-power fields. Vascular invasion was observed in 10 of 22 patients (45.5%). Extracapsular/extraskeletal infiltration into the surrounding tissues was assessed in 20 patients, with 14 of them (70%) showing infiltration beyond the tumor border. Regarding imaging of bone lesions, two patients had Ludwick type IIIB, whereas one patient had type II. The growth pattern of soft tissue lesions was well-defined in two patients (16.7%), focally invasive in seven patients (58.3%), and diffusely invasive in three (25.0%) out of 12 patients., Conclusion: Myoepithelial carcinoma of the bone and soft tissue presents high risk of local recurrence and distant metastasis. Histological and imaging features might be important to understand the aggressive behavior of the tumor., (© 2024. The Author(s), under exclusive licence to International Skeletal Society (ISS).)

Objective: No consensus exists for tumor volume response criteria in patients with Ewing sarcoma. This study aimed to identify an optimal cutoff for predicting a good histological response by analyzing tumor volume changes and tumor necrosis after neoadjuvant chemotherapy., Materials and Methods: We performed a retrospective analysis of 184 Ewing sarcoma patients, analyzing tumor volume changes before and after neoadjuvant chemotherapy. Patients were divided into two groups based on histological response: good (tumor necrosis ≥ 95%) and poor (tumor necrosis < 95%) responders. The receiver operating characteristic (ROC) area under the curve (AUC) method was used to determine the optimal thresholds for predicting the histological response. Additionally, the prognostic value of this cutoff for relapse-free survival was assessed., Results: Out of 184 patients, 83 (45%) had tumor necrosis ≥ 95%, while 101 (55%) had tumor necrosis < 95%. ROC analysis identified the optimal cutoff for a good histological response as over 65% tumor volume reduction (AUC = 0.69; p < 0.001). Patients with volume reduction of ≥ 65% had a higher likelihood of a good histological response than those with lesser reductions (p = 0.004; odds ratio = 2.61). Multivariable analysis indicated a correlation between poor histological response and reduced relapse-free survival (hazard ratio = 2.17; p = 0.01), while tumor volume reduction itself did not impact survival., Conclusion: We reported that a tumor volume reduction of ≥ 65% was able to predict a good histological response in Ewing sarcoma patients. We recommend preoperative tumor volume assessment to identify patients at greater risk for poor histological response who could benefit from more intensive chemotherapy protocols or additional radiotherapy., (© 2024. The Author(s), under exclusive licence to International Skeletal Society (ISS).)

Aneurysmal bone cyst (ABC) is a rare and usually painful condition, representing about 1% of all bone tumors. A geographical lytic, expansile, and septated radiological pattern, with fluid-fluid levels on MRI, is classically displayed. ABC can be a primary bone lesion (70% of patients) or can arise in an underlying condition and is subsequently named "ABC-like changes" (30%). ABC-like changes are more frequently encountered in skeletal segments affected by chondroblastoma, fibrous dysplasia, giant cell tumor, osteoblastoma, non-ossifying fibroma, and osteosarcoma. In this article, we describe the first case of ABC-like changes developed in association with an ultra-rare sclerosing bone disease: melorheostosis. Melorheostosis is characterized by recognizable patterns on radiological studies with a pathological increased bone density and a cortical thickening within the periosteal or endosteal space, usually with a "dripping candle wax" appearance. More rarely, other different radiological patterns can be observed, such as "osteopatia striata-like," "osteoma-like," "myositis ossificans-like," and mixed patterns. Pain and limb hypotrophy are the most common clinical manifestations. We report the case of a Caucasian male with a clinic-radiological diagnosis of melorheostosis (with epiphyseal osteopoikilosis) since the age of twelve. At the age of nineteen, he suffered from increased pain in the proximal right thigh, and the radiological control revealed an expansive septated lesion at the right proximal femoral bone. The diagnosis of ABC-like changes developed in melorheostosis was obtained after CT-guided bone biopsy and confirmed by open-incisional biopsy., (© 2023. The Author(s), under exclusive licence to International Skeletal Society (ISS).)

Pseudomyogenic haemangioendothelioma (epithelioid sarcoma-like haemangioendothelioma) is a recently described, rarely metastasising neoplasm of the soft tissues that often presents as multiple discontinuous nodules in different tissue planes of a limb. This tumour type is extremely difficult to diagnose because no morphological evidence suggestive of endothelial differentiation is present to confirm a radiological suspicion of vascular neoplasm. All but one case published in the literature underline that bone involvement is secondary to deep and superficial soft tissue nodules. Here, we report two cases of primary bone pseudomyogenic haemangioendothelioma occurring in the radius and cuboid bone with a multifocal presentation.

Hemangiopericytoma is a rare neoplasm. Primary meningeal hemangiopericytomas account for 1 to 7% of all meningeal tumors. In the literature, meningeal hemangiopericytomas are mainly case reports, which confirm an aggressive behavior with a high rate of local recurrence and extracranial metastasis. Metastasis can be seen many years after initial surgical excision of the primary tumor, and the most common sites include the bone, liver and lung. We present a pathological study of four meningeal hemangiopericytomas with bone metastases. All patients are male with a mean age of 46.5 years. Metastases only involved bone. Three out of four lesions were initially misdiagnosed as meningiomas. Only one case was initially correctly diagnosed as meningeal hemangiopericytoma. All patients underwent surgery with complete resection. Only the patient immediately diagnosed with meningeal hemangiopericytoma received postoperative radiation therapy. Three patients had bone metastases without local recurrence including the one who received radiation therapy. One patient recurred locally after 7 years, and bone metastasis was found at the same time. Our cases confirm that meningeal hemangiopericytomas are a separate entity and have a high recurrence rate despite complete surgical resection, with extracranial metastases, mainly to bone, even after long intervals.

The classification of vascular bone tumors remains challenging, with considerable morphological overlap spanning across benign to malignant categories. The vast majority of both benign and malignant vascular tumors are readily diagnosed based on their characteristic histological features, such as the formation of vascular spaces and the expression of endothelial markers. However, some vascular tumors have atypical histological features, such as a solid growth pattern, epithelioid change, or spindle cell morphology, which complicates their diagnosis. Pathologically, these tumors are remarkably similar, which makes differentiating them from each other very difficult. For this rare subset of vascular bone tumors, there remains considerable controversy with regard to the terminology and the classification that should be used. Moreover, one of the most confusing issues related to vascular bone tumors is the myriad of names that are used to describe them. Because the clinical behavior and, consequently, treatment and prognosis of vascular bone tumors can vary significantly, it is important to effectively and accurately distinguish them from each other. Upon review of the nomenclature and the characteristic clinicopathological, radiographic and genetic features of vascular bone tumors, we propose a classification scheme that includes hemangioma, hemangioendothelioma, angiosarcoma, and their epithelioid variants.