1/4 SM Musculoskelet Disord 5: 4 SM Musculoskeletal Disorders ISSN: 2576-5442 Submitted: 23 November 2021 | Accepted: 20 December 2021 | Published: 23 December 2021 *Corresponding author: Jefery Summers Jr.*, Department of Pathology, American University of the Caribbean School of Medicine, USA Copyright: © 2021 Summers J Jr., et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Citation: Summers J Jr., Allison E, Millon J, Wallace A, Jahoda J, et al. (2021) Low Grade Myofbroblastic Sarcoma of the Bone with Recurrence as a High Grade Sarcoma: Case Report and Review of the Literature. SM Musculoskelet Disord 5: 4. Low Grade Myofibroblastic Sarcoma of the Bone with Recurrence as a High Grade Sarcoma: Case Report and Review of the Literature Jefery Summers Jr.*, Elizabeth Allison, Jasmin Millon, Alec Wallace, Jessica Jahoda, Corey Steinman, Qi Yangyang, Mohamed Aziz MD Department of Pathology, American University of the Caribbean School of Medicine, USA Abstract High-grade myofbroblastic sarcoma (HGMS) is a rare malignancy characterized by a high rate of recurrence and metastasis. This form of malignancy tends to be indolent in nature and patients’ initial complaints are usually a painless mass. In this report, we present a case of a 40-year-old male who was initially evaluated for a left knee mass. Imaging studies and biopsy evaluation concluded the diagnosis of low- grade myofbroblastic sarcoma of the distal femur and surrounding soft tissue. Despite adherence to current treatment standards for this particular malignancy, the patient experienced recurrence requiring further surgical intervention, adjuvant chemotherapy and radiotherapy. Recurrent tumor was in the form of high-grade myofbroblastic sarcoma. After exhausting all available treatment options, the patient expired secondary to multi-organ failure associated with widespread metastases. In this report, we discuss how to diferentiate this sarcoma from other types of sarcomas and provide a brief review of the literature. Keywords: Myofbroblastic; Low grade; High grade; Recurrence; Chemotherapy Abbreviation LGMS: Low grade myofibroblastic sarcoma, HGMS: High-grade myofibroblastic sarcoma, MS: Myofibroblastic sarcomas, IMT: Inflammatory myofibroblastic tumor, IHC: Immunohistochemistry, MFH: malignant fibrous histiocytoma Introduction Myofibroblastic sarcomas (MS) are rare malignancies that have been better understood over the last few years; however, clearly defined diagnostic criteria have not been well developed (1). Myofibroblasts are defined as modified fibroblasts that are short, bi-or tripolar spindle-shaped or stellate cells, with a single, small, wavy or ovoid pale-staining nucleus with only a small amount of cytoplasm. Myofibroblasts have a contractile element and can synthesize collagens and other stromal components, including fibronectin and laminin. They are naturally part of the stroma of various tissues, including testicular peritubular stroma, the periodontal ligament, as well as inflammatory and reparative granulation tissue; however, they are also the principal cell type in some reactive and neoplastic soft-tissue lesions (2). These neoplasms, termed myofibroblastic sarcomas, are rare and typically originate throughout the body including the head, neck extremities and trunk and are classified based on their morphological characteristics into low, intermediate, and high grade (3). The current classification system for myofibroblastic sarcomas can be regarded as low, intermediate, and high-grade (4). Low grade myofibroblastic sarcoma (LGMS) are infiltrative tumors, usually located within deep soft tissue, and have a predilection for the head and neck region. These tumors display varied microscopic appearances, from fasciitis-like to fibrosarcoma-like, but they all, at least focally, display nuclear pleomorphism (3). However, no recurrent cytogenetic or molecular markers have been described thus far (5). LGMS express smooth-muscle actin and calponin, some express desmin, and most lack h-caldesmon. These sarcomas can recur but rarely metastasize. Inflammatory myofibroblastic tumor (IMT) and infantile fibrosarcomas can be regarded as two additional LGMS, which are usually seen in younger patients. IMTs typically arise in locations including the lung, retroperitoneum or mesentery (3). LGMS invade locally and are known to progress to high-grade sarcoma (6). LGMS are distinct from High-grade myofibroblastic sarcoma (HGMS), also called pleomorphic myofibrosarcoma, which are malignant fibrous histiocytoma (MFH)-like tumors. These are more frequently Actin positive than other MFH tumors (3). HGMS is diagnosed by cytomorphological analysis and immunohistochemistry (IHC) studies and has higher recurrence and metastatic rates than low-grade myofibroblastic sarcoma (7). A study of HGMS found that 29% of these tumors recurred, 71% metastasized, and 43% of patients died of disease. When compared with undifferentiated pleomorphic sarcomas, HGMS differentiation has better prognosis. Still, HGMS is a more aggressive tumor and has a worse prognosis than LGMS (3). Case Report © Summers J Jr., et al., 2021