Low-grade myofibroblastic sarcoma (LGMS) is a rare soft-tissue malignant neoplasm originating from the stromal cells that is predominantly comprised of atypical myofibroblasts. The present study reports the case of a patient with low-grade myofibroblastic sarcoma in the soft tissue of the knee. The patient exhibited a soft, painless mass on the medial side of the left knee. During surgery, a yellow-white mass above the posterior margin of the sartorius muscle was identified. This mass, which was irregular and adherent to surrounding tissues, had a blurry boundary, indicative of invasive growth. The morphology of the mass significantly differed from conventional lipomas and was lacking typical features. Immunohistochemical staining confirmed the diagnosis of a malignant LGMS. The patient experienced no recurrence over 1 year of follow-up and reported complete recovery of knee range of motion. The present study suggests that an incisional biopsy may be performed if LGMS is suspected based on patient symptoms and imaging results. In addition, long-term follow-up is crucial for the timely detection and management of any recurrence, playing a key role in the patient\'s ongoing care and treatment.

Low-grade central osteosarcoma is a rare subtype of tumor with low-grade malignancy. Currently, wide resection with negative resection margin is the standard treatment for this disease. The role of neoadjuvant chemotherapy in low-grade central osteosarcoma was controversial and was mostly considered for tumors containing high-grade focal areas. Local tumor recurrences often exhibited a tumor with higher histologic grade or differentiation with the potential for metastases. In low-grade central osteosarcoma, timely wide resection after definite diagnosis can result in 5-year survival for almost 90%. However, the relatively nonspecific radiological and pathological findings make diagnosis very difficult. MDM2 and CDK4 are specific and provide sensitive markers for the diagnosis of low-grade central osteosarcoma, helping to differentiate low-grade central osteosarcoma from some benign lesions, including fibrous dysplasia, bone giant cell tumor, and chondrosarcoma. Here, we report the case of a 19-year-old woman with low-grade central osteosarcoma located at the proximal humerus. The affected site was rare, but the sensitive biomarkers CDK4 and MDM2 were positive. The patient recovered well after wide tumor resection following a proximal humerus endoprosthesis replacement. Our case highlighted the management strategies in low-grade central osteosarcoma. Being familiar with radiographic features, understanding the biological characteristics, and mastering diagnostic biomarkers can help oncologists avoid embarrassing situations in treatment when this rare tumor is highly suspected, even when located at an uncommon site. The discussion in this report focuses on radiographic and pathological features, advances of biomarkers that help in differential diagnosis, and current treatment options in low-grade central osteosarcoma.

BACKGROUND: Soft tissue sarcomas are rare neoplasms that can occur in the thoracic wall, abdominal wall, extremities, and inguinal region. Wide local resection, with precise histological margin control, results in large skin defects that are challenging to close. Various repair procedures, such as vertical rectus abdominis flaps (VRAM), latissimus dorsi flaps, and tensor fascia lata (TFL) flaps are used to cover broad thoracic wall defects. Although the cosmetic reconstruction results of using these flaps are often excellent, each has significant drawbacks. The external oblique musculocutaneous flap is a simple and safe surgical procedure for covering thoracic wall defects.
OBJECTIVE: This study aimed to retrospectively assess the safety and technique of using the external oblique musculocutaneous flap to cover large thoracic wall defects after radical excision of locally advanced sarcomas in 20 patients at a single institution.
METHODS: From January 2006 to December 2016, 20 Chinese patients with large advanced sarcomas on their trunks received wide local resection, with precise histological negative margins. The external oblique musculocutaneous flap, mobilized from the ipsilateral abdominal wall, was harvested to cover broad thoracic wall defects.
RESULTS: Among the 20 sarcoma patients (12 females and 8 males, ranging in age from 25 to 73 years), there were five patients with primary tumors and 15 patients with recurrent tumors. The median tumor diameter was approximately 15.3 cm. After excising the lesion, the median time to cover the defect with the external oblique myocutaneous flap was 66 min. The average blood loss when harvesting the flap was approximately 48 mL. For the 20 patients in our cohort, the external oblique flap achieved closure of defects measuring an average area of 256 cm2 . No other flaps or reconstruction techniques were used to cover the large defects in this study. There were no deaths directly related to the flap reconstruction procedures.
CONCLUSIONS: The external oblique musculocutaneous flap was a safe and reliable method of covering broad thoracic wall defects after radical tumor excision.

The present report describes a case of a 44-year-old female patient who presented with a palpable mass of the left thigh. A diagnosis of parosteal osteosarcoma (POS) at the femoral diaphysis was made following a diagnostic workup. Previous reports of long bone diaphyseal POS are rare. A long diaphyseal segment of the femur containing the tumor was resected along with a healthy margin of soft tissues, and the damaged bone was reconstructed with a custom-made intercalary endoprosthesis. Subsequent pathological examination of the surgical sample confirmed the diagnosis of POS. No local recurrence or distant metastasis was observed, and the patient had a positive Musculoskeletal Tumor Society score of 28/30 (93.3%) at the 28-month post-surgery follow-up. The present study describes the clinical, radiological, and pathological features of this rare type of osteosarcoma.