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Aims: Anastomosing haemangiomas are benign tumours with anastomosing vascular channels that may mimic angiosarcoma. While anastomosing haemangiomas have been described in diverse locations, particularly the abdominal/paraspinal region, data on anastomosing haemangiomas in the mediastinum remain limited. We report the clinicopathological, radiological and molecular characteristics of the largest single‐institutional series of mediastinal anastomosing haemangiomas. Methods and results: In our pathology archives in 2011–23, we reviewed all vascular lesions involving the mediastinum and identified seven anastomosing haemangiomas. Clinical information was abstracted from medical charts; available radiological imaging was reviewed. Targeted DNA‐based next‐generation sequencing (447 genes, including GNAQ and GNA11) was performed on five cases. The seven patients included five women and two men, with an age range of 55–77 (median = 72) years. Of the six tumours with available radiology, two each were in the prevascular, visceral and paravertebral mediastinum, with lobulated peripheral enhancement in all tumours examined with contrast enhancement. Six patients underwent tumour resection; one patient received proton radiotherapy. Microscopically, each tumour was solitary and characterised by anastomosing capillary‐sized vessels lined by hobnail endothelial cells. Fibrin microthrombi, hyaline globules and extramedullary haematopoiesis were common. In the five tumours analysed by next‐generation sequencing, GNAQ p.Q209P was identified in one tumour; no additional reportable alterations were identified in the remaining cases. No recurrence was noted in the four patients with available follow‐up of 3–58 (median = 9.5) months after resection. Conclusion: While mediastinal anastomosing haemangiomas can microscopically mimic angiosarcoma, awareness of this entity and radiological correlation may help to circumvent this diagnostic pitfall. [ABSTRACT FROM AUTHOR]

Primary bone tumours can pose diagnostic problems due to their overlapping radiologic and histologic features. Given the recent advancement in our understanding of the biology of bone tumours, multiple immunohistochemical and molecular markers have been devised to aid in their diagnosis. This review provides brief updates on select bone tumours, including chondrosarcomas, benign chondrogenic tumours, osteosarcomas, benign osteogenic tumours, fibroosseous lesions, vascular tumours, osteoclastic giant cell‐rich or cystic tumours, chordoma, adamantinoma, small round blue cell sarcomas, and others. We discuss their salient molecular features and novel immunohistochemical correlates, along with some tips to avoid common diagnostic pitfalls. [ABSTRACT FROM AUTHOR]

Background and objectives: Bone tumours are relatively rare and, as a consequence, treatment in a centre with expertise is required. Current treatment guidelines also recommend review by a specialised pathologist. Here we report on international consensus‐based datasets for the pathology reporting of biopsy and resection specimens of bone sarcomas. The datasets were produced under the auspices of the International Collaboration on Cancer Reporting (ICCR), a global alliance of major (inter‐)national pathology and cancer organisations. Methods and results: According to the ICCR's process for dataset development, an international expert panel consisting of pathologists, an oncologic orthopaedic surgeon, a medical oncologist, and a radiologist produced a set of core and noncore data items for biopsy and resection specimens based on a critical review and discussion of current evidence. All professionals involved were bone tumour experts affiliated with tertiary referral centres. Commentary was provided for each data item to explain the rationale for selecting it as a core or noncore element, its clinical relevance, and to highlight potential areas of disagreement or lack of evidence, in which case a consensus position was formulated. Following international public consultation, the documents were finalised and ratified, and the datasets, including a synoptic reporting guide, were published on the ICCR website. Conclusion: These first international datasets for bone sarcomas are intended to promote high‐quality, standardised pathology reporting. Their widespread adoption will improve the consistency of reporting, facilitate multidisciplinary communication, and enhance comparability of data, all of which will help to improve management of bone sarcoma patients. [ABSTRACT FROM AUTHOR]

Aims: Simple bone cysts are benign intramedullary tumours primarily involving the long bones in skeletally immature individuals. Several mechanisms have been proposed for their pathogenesis. Although the diagnosis is typically straightforward, the interpretation can be problematic, because of superimposed fracture causing them to resemble aneurysmal bone cysts and other tumours. EWSR1–NFATC2 or FUS–NFATC2 fusions, which are characteristic of a subset of aggressive round cell sarcomas, have been recently detected in simple bone cysts. The aim of this study was to examine the clinicopathological and molecular features in a series of simple bone cysts. Methods and results: Using RNA‐based next‐generation sequencing and/or fluorescence in‐situ hybridisation, we investigated the presence of EWSR1 or FUS rearrangements in nine simple bone cysts. The patients were five females and four males, aged 3–23 years (median, 14 years); the tumours ranged from 19 mm to 160 mm (median, 46 mm) in size, and involved the femur (n = 3), humerus (n = 2), fibula (n = 2), tibia (n = 1), and iliac wing (n =1). We identified three cases with EWSR1–NFATC2 fusion (showing identical breakpoints to those in EWSR1–NFATC2 sarcomas) and one additional case with FUS rearrangement. Unlike in EWSR1–NFATC2 sarcomas, immunohistochemical expression of NKX3.1 and NKX2.2 was absent in two simple bone cysts tested. Conclusions: More than 40% of simple bone cysts harbour genetic alterations confirming that they are neoplastic, investigation of EWSR1 and/or FUS rearrangement may help to distinguish simple bone cysts from mimics, and NFATC2 rearrangement is not pathognomonic of malignancy. [ABSTRACT FROM AUTHOR]