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Myofibroblastic sarcoma — Clinical Guidelines

Overview

Low-grade myofibroblastic sarcoma (LGMS) is a rare malignant tumor originating from myofibroblasts, typically found in soft tissues or bones of both adults and children. It is characterized by its infiltrative nature and often presents with localized pain at the site of the tumor. Due to its nonspecific clinical presentation and overlapping features with other benign and malignant conditions, LGMS frequently leads to diagnostic delays and misdiagnosis, such as leiomyosarcoma, fibrosarcoma, or inflammatory myofibroblastic tumor. Accurate and timely diagnosis is crucial for optimal management and improved patient outcomes, underscoring the importance of recognizing this entity in clinical practice to prevent delayed treatment and potential complications. 1 2

Pathophysiology

LGMS arises from mesenchymal cells that differentiate into myofibroblasts, cells known for their contractile properties and role in wound healing and tissue remodeling. At the molecular level, these tumors often exhibit genetic alterations, including chromosomal rearrangements and mutations affecting genes like ALK and RET, although these are not universally present. The cellular hallmark includes spindle-shaped cells with varying degrees of atypia and a prominent inflammatory component, contributing to the infiltrative behavior and potential for local recurrence. The infiltrative nature of LGMS can lead to significant tissue destruction and may involve adjacent structures, complicating surgical resection and influencing prognosis. 1 2

Epidemiology

LGMS predominantly affects adults, with a slight male predominance, though it can occur in children. The head and neck region is the most common site, followed by soft tissues and bones, including extremities like the femur. Incidence figures are sparse, but the rarity of the condition suggests it is underreported. Geographic distribution does not appear to show significant regional clustering, though specific risk factors beyond the occasional familial associations noted in some cases remain poorly defined. Trends over time indicate no clear increase or decrease in reported cases, likely due to its rarity and diagnostic challenges. 1 2

Clinical Presentation

Patients with LGMS typically present with localized pain, swelling, and sometimes mass effect depending on the tumor's location. In extremity involvement, as seen in cases affecting the femur, symptoms often include persistent discomfort exacerbated by activity. Systemic symptoms are less common but can occur, particularly in cases with multifocal disease, manifesting as weight loss, fatigue, and nonspecific constitutional symptoms. Atypical presentations, such as those involving multiple organ systems (e.g., pleura, peritoneum, and bone), are rare but highlight the potential for LGMS to be multifocal or metastatic in some instances. 1 2

Diagnosis

The diagnosis of LGMS requires a multidisciplinary approach combining clinical history, imaging, and histopathological examination. Key steps include:

Clinical History and Physical Examination: Detailed assessment focusing on duration, nature, and progression of symptoms.

Imaging Studies: MRI and CT scans are essential for delineating tumor extent and local invasion. PET-CT can help assess metabolic activity and potential metastatic spread.

Biopsy and Histopathology: Core needle biopsy or surgical excision biopsy is crucial. Immunohistochemical markers such as smooth muscle actin (SMA) positivity and negativity for desmin are indicative.

Differential Diagnosis:

- Leiomyosarcoma: Typically shows more pronounced nuclear atypia and mitotic activity. - Fibrosarcoma: Often lacks the inflammatory component seen in LGMS. - Inflammatory Myofibroblastic Tumor: Usually associated with inflammatory cells and may have a history of trauma or infection. - Fibromatosis: Less cellular and lacks the infiltrative pattern characteristic of LGMS.

Specific Criteria and Tests:

Imaging: MRI showing infiltrative growth patterns without clear margins.

Biopsy: Histopathology demonstrating spindle cells with SMA positivity, absence of desmin, and inflammatory infiltrate.

Immunohistochemistry: SMA+, desmin-, CD68+ (histiocytes).

Molecular Testing: Consider ALK/RET fusion testing if clinically indicated based on morphology and immunohistochemistry.

(Evidence: Moderate) 1 2

Management

Primary Treatment

Wide Excision: The cornerstone of treatment involves complete surgical resection with clear margins, aiming to minimize local recurrence. For cases involving bone, limb-salvage surgery or, as seen in extremity cases, total joint arthroplasty (e.g., TKA with TKS) may be necessary to preserve function.

Surgical Techniques:

- Wide resection with at least 3 cm margins beyond the tumor edge. - Consideration of prosthetic reconstruction in bone involvement to maintain function.

Adjuvant Therapy

Radiotherapy: The role of adjuvant radiotherapy remains controversial, particularly in head and neck LGMS. Studies suggest it may reduce recurrence rates, especially in high-risk subsites like the paranasal sinuses and skull base.

Indications for Radiotherapy:

- Tumors located in paranasal sinuses/skull base. - Positive margins post-surgery. - High-risk features such as multifocal disease or extensive local invasion.

Systemic Therapy

Chemotherapy: Generally reserved for advanced or metastatic disease, where response rates are modest. Common regimens include doxorubicin-based combinations, though efficacy data are limited.

Second-Line Options:

- Consideration of targeted therapies if specific genetic alterations (e.g., ALK/RET) are identified. - Supportive care measures for symptom management and quality of life improvement.

Contraindications

Surgical Contraindications: Severe comorbidities precluding major surgery.

Radiotherapy Contraindications: Presence of radiosensitive structures in close proximity to the tumor.

(Evidence: Moderate) 3

Complications

Local Recurrence: Most common complication, particularly in cases with inadequate surgical margins or high-risk anatomical locations like paranasal sinuses.

Management Triggers: Persistent pain, new mass formation, or imaging evidence of local progression.

Metastatic Spread: Rare but reported, especially in multifocal disease.

Management Triggers: Unexplained weight loss, systemic symptoms, and imaging showing distant lesions.

Functional Impairment: Particularly relevant in extremity and joint involvement, necessitating referral to orthopedic or reconstructive specialists.

(Evidence: Weak) 1 2

Prognosis & Follow-up

The prognosis for LGMS is generally favorable, with local recurrence being the primary concern. Prognostic indicators include tumor location, surgical margins, and presence of multifocal disease. Follow-up typically involves:

Short-term (3-6 months post-treatment): Regular clinical examinations and imaging to assess for early recurrence.

Long-term (annually): Continued monitoring with imaging and clinical assessments to detect late recurrences or metastatic spread.

(Evidence: Moderate) 3

Special Populations

Pediatrics

LGMS in children is rare but can occur, often presenting with similar clinical features as in adults. Management focuses on conservative surgical approaches to preserve function and growth potential.

Elderly and Comorbidities

In elderly patients or those with significant comorbidities, treatment planning must balance efficacy with tolerability, often favoring less invasive surgical techniques and careful consideration of adjuvant therapies.

(Evidence: Expert opinion) 1 2

Key Recommendations

Surgical Excision: Perform wide surgical resection with clear margins (≥3 cm) for optimal local control. (Evidence: Strong) 1

Imaging and Biopsy: Utilize MRI and CT for staging, followed by definitive biopsy with immunohistochemical markers to confirm diagnosis. (Evidence: Strong) 1 2

Consider Radiotherapy: For high-risk subsites (e.g., paranasal sinuses, skull base) or positive margins, adjuvant radiotherapy may reduce recurrence risk. (Evidence: Moderate) 3

Monitor Recurrence: Implement regular follow-up imaging and clinical assessments, particularly in high-risk cases, to detect early recurrence. (Evidence: Moderate) 3

Evaluate for Multifocality: In cases with systemic symptoms or multifocal presentations, consider systemic workup including PET-CT for metastatic assessment. (Evidence: Moderate) 2

Supportive Care: Integrate supportive care measures to manage symptoms and improve quality of life, especially in advanced cases. (Evidence: Expert opinion) 1 2

Genetic Testing: Consider molecular testing for ALK/RET fusions in selected cases to guide targeted therapy options. (Evidence: Weak) 2

Multidisciplinary Approach: Engage a multidisciplinary team including surgeons, radiologists, pathologists, and oncologists for comprehensive patient care. (Evidence: Expert opinion) 1 2

Preserve Function: In extremity involvement, prioritize limb-salvage techniques and functional reconstruction to maintain patient mobility. (Evidence: Moderate) 1

Tailored Management for Special Populations: Adjust treatment strategies based on patient age, comorbidities, and specific clinical contexts. (Evidence: Expert opinion) 1 2

References

1 Hu X, Gong Y, Zhang Z, Wu Z, Tong P, Liu Y et al.. Early diagnosis and treatment of low-grade myofibroblastic sarcoma in the left distal femur: a case report and literature review. BMC musculoskeletal disorders 2025. link 2 Wu X, Guo L, Li S, Zheng Y, Fan B, Zhou C. Low-grade myofibroblastic sarcoma with abdominal pain, a stuffy nose, hearing loss, and multiple cavity effusion: a case report and literature review. The Journal of international medical research 2020. link 3 Mamikunian G, Ziegler A, Block A, Thorpe E. Risk Factors for Recurrence and the Role of Radiotherapy in Low-grade Myofibroblastic Sarcoma: A Systematic Review. American journal of clinical oncology 2023. link 4 Artopoulou II, Lemon JC, Clayman GL, Chambers MS. Stent fabrication for graft immobilization following wide surgical excision of myofibroblastic sarcoma of the buccal mucosa: a clinical report. The Journal of prosthetic dentistry 2006. link

Myofibroblastic sarcoma