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Parosteal osteosarcoma is an uncommon, low-grade, well differentiated malignant bone neoplasm with a more favorable prognosis compared to other types of osteosarcoma. Dedifferentiation is a well-known phenomenon, observed in 16–24.6 % of cases, leads to a combination of low-grade fibroblastic osteosarcoma and high-grade sarcoma. The dedifferentiated component is typically high-grade conventional osteosarcoma, although unusual variants such as spindle cell sarcoma, telangiectatic osteosarcoma, and rhabdomyosarcomatous dedifferentiation may arise. This case report contributes significant information to the sparse literature on dedifferentiated parosteal osteosarcoma due to its distinctive characteristics. We describe a rare presentation of dedifferentiated parosteal osteosarcoma in a 44-year-old male with a lesion in the left femur. The dedifferentiated component included low-grade leiomyosarcoma alongside high-grade conventional osteosarcoma, presenting a diagnostic challenge, particularly with limited biopsy material. Diagnosis was confirmed using fluorescence in situ hybridization (FISH) for MDM2 gene amplification, emphasizing the importance of molecular diagnostic testing in such complex cases. This case highlights a rare presentation of dedifferentiated parosteal osteosarcoma (DPO) with low-grade leiomyosarcomatous and high-grade osteosarcomatous components, posing significant diagnostic challenges. Accurate diagnosis required a multidisciplinary approach, including imaging, histopathology, and MDM2 gene amplification testing, especially given the limitations of initial biopsy samples. Early recognition of dedifferentiation is critical due to its impact on metastasis risk and treatment planning. The case underscores the need for personalized treatment strategies and vigilant long-term follow-up in managing rare bone tumors like DPO. This case presenting a distinctive pattern of dedifferentiation is, to our knowledge, the first documented case of low-grade leiomyosarcoma occurring in parosteal osteosarcoma. As it enhances the clinical understanding by broadening the range of dedifferentiated components identified in parosteal osteosarcoma and highlights the diagnostic difficulties associated with these uncommon bone tumors. • Parosteal osteosarcoma (PO) often has a favorable prognosis but may dedifferentiate, significantly increasing its clinical complexity. • Presented a rare dedifferentiated PO case in a 44-year-old male with low-grade leiomyosarcoma, emphasizing unique diagnostic challenges. • Emphasized the importance of recognizing dedifferentiation in PO for appropriate management. [ABSTRACT FROM AUTHOR]

A revision rotator cuff repair is a technically challenging surgical procedure. This can be further complicated by the presence of poor quality of the cuff tissue, as well as a large greater tuberosity cyst, typically located at the rotator cuff footprint. This Technical Note discusses the surgical approach to deal with a revision rotator cuff tear with a large humeral head cyst. This described arthroscopic technique is performed in a single-stage procedure using a human dermal allograft (GraftJacket) for augmentation. This technique was specifically designed to (1) address the limited area for anchor placement, (2) use a bone graft, demineralized bone matrix, for repairing the bone cyst, and (3) optimize the biology for healing by augmenting the reconstruction with GraftJacket. [ABSTRACT FROM AUTHOR]