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Synovial hemangioma, a rare benign tumor that occurs most frequently in the knee in children and young adults, has four histological subtypes: Venous, arteriovenous, cavernous and capillary hemangiomas. Since the clinical presentation and radiological findings of synovial hemangioma are non-specific, there is frequently a long period between the onset and the diagnosis. The cases of nine patients, pathologically diagnosed with synovial hemangioma and surgically treated, were retrospectively analyzed. All nine patients had persistent knee pain. In addition, three patients also had a swollen knee with intra-articular hemorrhage. Plain radiography revealed intra-articular phleboliths in two patients. In seven patients, T1-weighted magnetic resonance imaging showed low signal intensity with small signal voids. On T2-weighted imaging, all patients showed high signal intensity containing small signal voids. All patients underwent surgical excision; there was no postoperative recurrence after the final operation, and the knee pain had disappeared at the final follow-up. From the pathological findings, the diagnoses were venous hemangioma, cavernous hemangioma and capillary hemangioma (three patients each). [ABSTRACT FROM AUTHOR]

Atypical lipomatous tumors (ALTs) are locally aggressive adipocytic malignancies that frequently occur in middle-aged adults. We report the rare case of an ALT of the thigh that occurred in a 4-year-old girl. Since the tumor was initially diagnosed as a lipoblastoma by incisional biopsy, marginal resection was performed. Histopathological findings of the surgical specimen revealed the proliferation of mature and variously sized adipocytes, as well as ectopic ossification; these features differ from the typical findings of lipoblastoma. Immunohistochemical findings showed nuclear positivity for a murine double minute 2 (MDM2) and cyclin-dependent kinase 4 (CDK4) and negativity for pleomorphic adenoma gene 1 (PLAG1). Fluorescence in situ hybridization showed abnormal amplification of the MDM2 gene. The patient was thus finally diagnosed as having an ALT. No signs of local recurrence or metastasis were noted 1 year postoperatively. This case is instructive in the differential diagnosis of primary adipocytic tumors. Lipoblastomas are the most common adipocytic tumors in children, but if a tumor is located in the deep tissue or imaging findings are not typical, the possibility of ALT should be considered and immunohistochemistry for MDM2 and CDK4 should be added., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2024 Ogawa, Hakozaki, Kaneuchi, Suzuki, Nikaido, Yamada, Utsumi, Hasegawa, Sano and Matsumoto.)