Overview
Synovial sarcoma (SS) is a rare, aggressive malignant soft tissue sarcoma accounting for approximately 5–10% of all soft tissue sarcomas. Despite its name, it does not arise from the synovium (the lining of joints) but from primitive mesenchymal cells capable of epithelial differentiation. It is defined molecularly by a specific chromosomal translocation, t(X;18)(p11.2;q11.2), resulting in the SS18-SSX fusion gene.
It predominantly affects adolescents and young adults (ages 15–40), with a slight male predominance. While it can occur anywhere in the body, it has a distinct predilection for the extremities, particularly around the knee joint (popliteal fossa), though it rarely involves the joint space itself.
Synovial sarcoma is a high-grade malignancy with a significant risk of local recurrence and distant metastasis (most commonly to the lungs). Early diagnosis and multidisciplinary management are critical for optimal outcomes.
Epidemiology & Risk Factors
| Parameter | Details |
|---|---|
| Incidence | ~1–3 cases per 1,000,000 people per year. |
| Age Distribution | Bimodal peak: Adolescents/Young Adults (15–40 yrs); rare in children <10 and elderly >60. |
| Gender Ratio | Male : Female ≈ 1.2 : 1. |
| Anatomic Distribution | Lower Extremity: ~50–60% (Thigh, Popliteal fossa, Foot/Ankle).<br>Upper Extremity: ~20–25%.<br>Trunk/Head/Neck/Visceral: ~15–20%. |
| Known Risk Factors | None established. No strong links to environmental exposures, trauma, or hereditary syndromes (unlike Li-Fraumeni or Neurofibromatosis type 1 associated sarcomas). Radiation therapy for prior malignancy is a rare antecedent (radiation-induced sarcoma). |
Pathogenesis & Molecular Biology
The hallmark of synovial sarcoma is a balanced reciprocal translocation between chromosomes X and 18:
t(X;18)(p11.2;q11.2)
This fuses the SS18 (SYT) gene on chromosome 18 with one of three SSX genes (SSX1, SSX2, SSX4) on chromosome X.
- SS18-SSX1 Fusion: Historically associated with biphasic histology and potentially slightly worse prognosis.
- SS18-SSX2 Fusion: Historically associated with monophasic fibrous histology.
- SS18-SSX4 Fusion: Rare.
The resulting fusion protein acts as an aberrant transcriptional regulator, disrupting chromatin remodeling complexes (BAF/SWI/SNF) and dysregulating developmental pathways (e.g., Wnt/β-catenin, SOX2), driving oncogenesis.
Histological Classification (WHO 2020)
Synovial sarcoma is categorized by microscopic appearance. All subtypes share the same molecular translocation and carry a similar malignant potential.
| Subtype | Description | Frequency | Key Microscopic Features |
|---|---|---|---|
| Monophasic (Fibrous) | Composed solely of spindle cells. | ~60–70% | Uniform spindle cells in fascicles; variable cellularity; “hemangiopericytoma-like” staghorn vessels; foci of calcification common. |
| Biphasic | Contains both spindle cells and epithelial cells. | ~20–30% | Distinct glandular/epithelial structures (tubules, papillae) lined by cuboidal/columnar cells adjacent to spindle cell areas. |
| Poorly Differentiated (High-Grade) | High-grade morphology; loses typical patterns. | ~5–10% | Solid sheets of round/epithelioid cells; high mitotic rate (>10/10 HPF); necrosis; may mimic Ewing sarcoma or melanoma. Requires IHC/Molecular confirmation. |
Diagnostic Pitfall:** The monophasic variant is frequently misdiagnosed as a benign fibrous tumor (fibroma, nodular fasciitis), solitary fibrous tumor, or malignant peripheral nerve sheath tumor (MPNST).
⚕️ How Does It Look? (Clinical, Imaging & Gross Pathology)
This section details the phenotypic presentation across clinical examination, radiology, and gross pathology.
1. Clinical Appearance (Physical Examination)
- Presentation: Typically a deep-seated, slow-growing mass.
- Consistency: Firm to hard, often fixed to underlying fascia or muscle (not freely mobile).
- Size at Diagnosis: Median 5–8 cm; often larger in proximal thigh/buttock (>10 cm) due to silent growth.
- Skin Changes: Usually intact. Overlying skin may be tethered or show venous dilation in large tumors. Ulceration is rare but signifies advanced disease/neglect.
- Neurovascular Signs: Tinel’s sign or neuropathic pain if compressing a nerve (common in popliteal fossa/foot). Pulse usually preserved unless massive vascular encasement.
- Lymphadenopathy: Regional lymph node metastasis is uncommon (<5–10%) but palpable nodes warrant immediate biopsy.
2. Radiological Appearance (Imaging Characteristics)
Imaging is essential for local staging (T-stage), surgical planning, and detecting skip metastases.
Magnetic Resonance Imaging (MRI) – Gold Standard for Local Staging
| Sequence / Feature | Typical Appearance |
|---|---|
| T1-Weighted | Hypointense to isointense relative to muscle. Key: Often shows “Triple Sign” (see below). |
| T2-Weighted | Markedly hyperintense (fluid-bright) due to high water content in epithelial/glandular areas (biphasic) or myxoid stroma (monophasic). Heterogeneous signal due to hemorrhage/necrosis/fibrosis. |
| T1 Post-Contrast (Gd) | Heterogeneous, often intense enhancement. Necrotic/cystic areas do not enhance. |
| Triple Sign (Pathognomonic but not 100% sensitive) | Three distinct signal intensities on T2:<br>1. High signal (cystic/epithelial/myxoid)<br>2. Intermediate signal (solid cellular/spindle cell)<br>3. Low signal (fibrous septa/calcification/hemosiderin). |
| Calcifications | Seen in ~30% on CT/MRI (blooming artifact on GRE/SWI). “Stippled” or “flocculent.” |
| Invasion | Assess fascial breach, neurovascular bundle encasement (>180° = likely invasion), bone erosion. |
Computed Tomography (CT) – Chest Staging & Bone Detail
- Primary Tumor: Excellent for detecting calcifications (confirming diagnosis vs. other sarcomas).
- Chest CT (Thin-cut, 1–3mm): Mandatory for baseline pulmonary metastasis screening. Detects nodules >2–3mm.
- Bone: Assesses cortical destruction or medullary invasion if tumor abuts bone.
Ultrasound (US) – Initial Triage
- Hypoechoic/heterogeneous mass with internal vascularity (Doppler+).
- Limitation: Cannot reliably assess deep fascial planes or neurovascular involvement. Not sufficient for surgical planning.
PET-CT (FDG-Avid)
- High SUVmax (typically >4–6, often 8–15).
- Role: Baseline metabolic staging, assessing treatment response (neoadjuvant therapy), surveillance for recurrence. Not specific (inflammation/infection also avid).
Table: Differential Diagnosis on Imaging
| Mimic | Key Differentiating Features |
|---|---|
| Malignant Peripheral Nerve Sheath Tumor (MPNST) | Arises from major nerve/plexus; “Target sign” on T2 (central low signal); often in NF1 patients. |
| Myxoid Liposarcoma | Fat signal on T1 (even minimal); “Chicken-wire” vessels; younger adults; DDIT3 rearrangement. |
| Epithelioid Sarcoma | Distal extremity (hand/forearm); central necrosis/ulceration (“geographic” necrosis); INI1/SMARCB1 loss. |
| Solitary Fibrous Tumor | STAT6 nuclear positivity; “Patternless pattern”; often pleural/meningeal; NAB2-STAT6 fusion. |
| Hemangioma / Vascular Malformation | Flow voids on MRI; phleboliths (calcifications); Doppler US diagnostic. |
| Abscess / Hematoma | Clinical context (fever, trauma); rim enhancement; diffusion restriction (abscess); evolves over time. |
3. Gross Pathology (Macroscopic Appearance)
- Encapsulation: Often pseudoencapsulated (compressed reactive tissue), not a true capsule. Shelling out = positive margins (R1/R2).
- Cut Surface: Tan-white to gray, firm, fleshy.
- Heterogeneity: Cystic spaces (glandular differentiation), hemorrhage, necrosis (high grade), calcifications (gritty texture).
- Size: Correlates with T-stage (T1 ≤5cm, T2 >5cm).
🩺 Symptoms
Symptoms are often insidious, leading to a median diagnostic delay of 6–18 months. The clinical picture depends heavily on anatomical location.
1. Local Symptoms (Primary Tumor)
| Symptom | Frequency | Clinical Nuance |
|---|---|---|
| Painless Mass | Most Common (~60–70%) | Often noticed incidentally or after minor trauma draws attention to area. |
| Pain / Tenderness | ~30–40% | Deep, dull, aching. Worse at night or with activity. Suggests nerve compression, periosteal irritation, or rapid growth/stretch of fascia. Night pain is a red flag for malignancy. |
| Neurological Deficits | ~15–25% (Location dependent) | Popliteal fossa: Sciatic/peroneal nerve palsy (foot drop), numbness lateral leg/foot.<br>Foot/Ankle: Plantar nerve compression (tarsal tunnel-like symptoms).<br>Brachial plexus/Neck: Radiculopathy, Horner’s syndrome. |
| Vascular Symptoms | Rare | Leg swelling (venous compression), claudication (arterial compression), ischemic changes. |
| Joint Dysfunction | Variable | Stiffness, reduced ROM if near joint (knee, ankle). Effusion is rare (intra-articular origin is extremely rare). |
| Pathological Fracture | Very Rare | Only with significant cortical bone destruction. |
2. Systemic & Metastatic Symptoms (Advanced Disease)
- Pulmonary Metastases (Lungs – #1 site):
- Asymptomatic (found on surveillance CT) – Most common.
- Cough, dyspnea, hemoptysis, pleuritic chest pain (late/large burden).
- Skeletal Metastases: Bone pain, pathological fracture.
- Lymph Node Metastases: Palpable regional nodes (inguinal, popliteal, axillary).
- Constitutional Symptoms: Weight loss, fatigue, low-grade fever, anorexia (late stage, high tumor burden).
3. “Red Flag” Symptom Cluster Requiring Urgent Referral
Any deep mass > 5 cm (golf ball size) OR any mass growing in size OR deep mass fixed to fascia/muscle OR mass with neurological symptoms OR recurrent mass after previous excision. Action: Urgent referral to a Sarcoma Multidisciplinary Team (MDT) / Specialist Center.** Do not excise in non-specialist setting without prior MRI and core needle biopsy.
Diagnosis: The Diagnostic Pathway
- Clinical Suspicion (History + Exam + Red Flags).
- Imaging: MRI of primary site (with contrast) + CT Chest/Abdomen/Pelvis (Staging).
- Biopsy: Core Needle Biopsy (Image-guided – US or CT) is standard.
- Contraindication: Incisional/Excisional biopsy before referral (contaminates planes, upstages to R1/R2, compromises limb salvage).
- Sample Requirements: Adequate tissue for Histology + IHC + Molecular Genetics (FISH/RT-PCR/NGS for SS18-SSX).
- Histopathology & Immunohistochemistry (IHC) Panel:
- Positive: TLE1 (Highly sensitive/specific), EMA (Epithelial Membrane Antigen – highlights epithelial component), Cytokeratins (AE1/AE3, CAM5.2), BCL2, CD99 (often focal), SOX10 (occasionally).
- Negative/Negative Help: S100 (usually negative/focal – helps r/o MPNST/Melanoma), Desmin/Myogenin (negative – r/o Rhabdomyosarcoma), STAT6 (negative – r/o SFT), INI1/SMARCB1 (retained – r/o Epithelioid Sarcoma/Rhabdoid).
- Molecular Confirmation: FISH (SS18 break-apart probe) or RT-PCR/NGS (SS18-SSX fusion transcript). Gold standard for diagnosis.
Staging Systems
AJCC 8th Edition (UICC) – TNM Staging for Soft Tissue Sarcoma (Trunk/Extremities)
| Stage | T (Size/Depth) | N (Nodes) | M (Mets) | Grade (G) |
|---|---|---|---|---|
| IA | T1 (≤5 cm) | N0 | M0 | G1 (Low) |
| IB | T2, T3, T4 (>5 cm) | N0 | M0 | G1 (Low) |
| II | T1 (≤5 cm) | N0 | M0 | G2/G3 (High) |
| IIIA | T2 (>5 cm) | N0 | M0 | G2/G3 (High) |
| IIIB | T3/T4 (>15cm / Invades bone/vessels) | N0 | M0 | G2/G3 (High) |
| IV | Any T | N1 | M1 | Any G |
Note: Synovial Sarcoma is Grade 2 or 3 (High Grade) by definition (FNCLCC system). Therefore, localized disease is always at least Stage II or III.
Treatment: Multidisciplinary Management
Treatment must be coordinated by a Sarcoma MDT (Surgeon, Radiation Oncologist, Medical Oncologist, Radiologist, Pathologist, Nurse Specialist).
1. Surgery – Primary Curative Modality
- Goal: Wide surgical excision (R0 resection) with negative microscopic margins (>1mm or fascial barrier).
- Limb Salvage: Achievable in >90-95% of extremity cases.
- Amputation: Reserved for major neurovascular encasement, infection, pathological fracture, or failed limb salvage.
- Margins:
- R0 (Wide): No tumor at ink. Standard.
- R1 (Microscopic positive): Post-op RT mandatory.
- R2 (Macroscopic positive): Re-resection if feasible.
2. Radiation Therapy (RT)
- Indication: Standard for all high-grade tumors >5cm (T2+). Strongly considered for high-grade <5cm (T1) due to high local recurrence risk (LRR) of SS.
- Timing:
- Preoperative (Neoadjuvant): 50 Gy / 25 fractions. Pros: Lower dose/volume, smaller field, permits assessment of response. Cons: Higher wound complication rate (~30-35%).
- Postoperative (Adjuvant): 60–66 Gy / 30–33 fractions (boost to tumor bed). Pros: Better wound healing. Cons: Higher dose to normal tissue, fibrosis, joint stiffness.
- Technique: IMRT/VMAT (Intensity Modulated) standard to spare bone/growth plates/nerves.
3. Systemic Therapy (Chemotherapy / Targeted / Immuno)
- Neoadjuvant (Pre-op) Chemotherapy:
- Controversial / Individualized. Standard for high-risk (Size >5cm, High Grade, Deep).
- Regimen: Doxorubicin + Ifosfamide (AI / IA / MAID). Ifosfamide adds specific activity in SS.
- Goal: Downsize tumor (facilitate R0), treat micromets, assess chemosensitivity (pathologic response >90% necrosis = good prognostic sign).
- Adjuvant (Post-op) Chemotherapy:
- No universal survival benefit proven in RCTs (unlike osteosarcoma/Ewing).
- Considered for high-risk patients (Large, Deep, High Grade, Young age) after MDT discussion. Shared decision-making essential.
- Metastatic/Advanced Disease:
- 1st Line: Doxorubicin +/- Ifosfamide (or Gemcitabine/Docetaxel).
- 2nd Line+: Pazopanib (FDA/EMA approved for non-adipocytic STS), Trabectedin (EU approved, specific activity in translocation-related sarcomas), Gemcitabine/Docetaxel, High-dose Ifosfamide.
- Targeted/Novel: TYK2 inhibitors, HDAC inhibitors, EZH2 inhibitors, Immunotherapy (CPI) trials. SS expresses NY-ESO-1 (CTAG1B) – target for TCR-engineered T-cell therapy (Afamitresgene autoleucel – FDA approved 2024 for HLA-A*02:01+ SS).
4. Management of Oligometastatic Disease
- Pulmonary Metastasectomy (Thoracoscopic/Open): Standard of care for resectable, controlled primary, adequate pulmonary reserve, long disease-free interval (>12-24 mo). Can achieve long-term survival/cure in ~20-30% selected patients.
- SBRT (Stereotactic Body RT): Non-surgical alternative for inoperable/oligoprogressive lung mets.
Follow-Up & Surveillance
High risk of late recurrence (up to 10–15+ years). Lifelong surveillance recommended.
| Timeframe | Clinical Exam | Imaging (Chest) | Imaging (Primary Site) |
|---|---|---|---|
| Years 1–2 | Every 3 months | Chest CT every 3–6 months | MRI primary site every 6 months (or per RT field) |
| Years 3–5 | Every 4–6 months | Chest CT every 6–12 months | MRI annually (or symptom-driven) |
| Years 5–10+ | Every 6–12 months | Chest CT annually (consider low-dose) | MRI annually / biennially |
| Lifelong | Annual | Annual Chest CT (or CXR if low risk) | As clinically indicated |
Late Effects Monitoring: Cardiac function (Echo/MUGA – Anthracycline cardiotoxicity), Renal function (Ifosfamide), Secondary malignancies, Lymphedema, Joint stiffness/fibrosis, Psychosocial support.
Prognosis & Prognostic Factors
Overall 5-Year Survival: ~60–75% (Localized disease).
10-Year Survival: ~50–60% (Late metastases occur).
Favorable Factors
- Tumor size ≤ 5 cm (T1).
- Superficial location (above fascia).
- Monophasic / SS18-SSX2 fusion type (some studies).
- R0 Resection achieved.
- Good histologic response to neoadjuvant chemo (>90% necrosis).
- Age < 25–30 years (controversial, some data better).
- Distal extremity (foot/hand) vs. Proximal (thigh/buttock).
Unfavorable Factors
- Tumor size > 5 cm (T2/T3), > 10 cm worse.
- Deep location (intramuscular/intermuscular).
- Biphasic / SS18-SSX1 fusion type (some data).
- Positive Margins (R1/R2).
- Metastasis at diagnosis (Stage IV).
- Older age (>40–50 yrs).
- Proximal location (Thigh, Buttock, Trunk, Head/Neck).
- High mitotic count / Necrosis (FNCLCC Grade 3).
Special Clinical Scenarios
1. Pediatric Synovial Sarcoma
- Biology similar to adults.
- Treatment: Same multimodal approach.
- Nuance: Radiation timing/dose critical (growth plate preservation, secondary malignancy risk). Limb growth preservation prioritized. Chemotherapy protocols often more intensive (pediatric trials – e.g., EpSSG, COG).
2. Synovial Sarcoma of Unusual Sites
- Head & Neck: Parapharyngeal space, orbit, larynx. Complex anatomy requires skull base/ENT/neurosurgery MDT. RT often primary or adjuvant due to margin constraints.
- Visceral (Lung, Heart, Kidney, GI, Mediastinum): Rare. Diagnosis often delayed. Surgery + systemic therapy mainstay.
- Intravascular (Intravascular Synovial Sarcoma): Extremely rare, aggressive.
3. Pregnancy
- Rare but documented.
- Diagnosis: MRI (no gadolinium unless essential), Core biopsy safe.
- Management: MDT decision. Surgery possible in 2nd trimester. Chemo (Doxorubicin/Ifosfamide) contraindicated 1st trimester; possible 2nd/3rd with counseling. RT contraindicated. Delivery planning critical.
Patient Resources & Support
- Sarcoma UK / Sarcoma Foundation of America (SFA) / Cancer Research UK: Patient information booklets, helplines, financial grants.
- ClinicalTrials.gov / EU Clinical Trials Register: Search “Synovial Sarcoma” for active trials (Targeted therapy, Immunotherapy, TCR-T).
- Specialist Sarcoma Centers: Treatment at high-volume centers (>50 sarcoma resections/year) improves outcomes. Ask for referral.
- Psychosocial: Sarcoma-specific support groups (online/in-person), fertility preservation counseling (pre-chemo/RT), genetic counseling (though not hereditary, de novo mutation).
Frequently Asked Questions (FAQ)
Q: Is Synovial Sarcoma hereditary?
A: No. The SS18-SSX translocation is a somatic (acquired) mutation occurring randomly in a single cell. It is not passed to children. Genetic testing of family members is not indicated.
Q: Why is it called “Synovial” Sarcoma if it doesn’t come from the joint lining?
A: Historical misnomer. Early pathologists noted the biphasic pattern resembled developing synovium. We now know the cell of origin is a mesenchymal stem/progenitor cell. The name persists for historical continuity.
Q: Can a “benign” synovial sarcoma exist?
A: No. There is no benign variant. All tumors with the SS18-SSX translocation are malignant. “Benign synovial sarcoma” is an obsolete term.
Q: Does the fusion type (SSX1 vs SSX2) change treatment?
A: Not currently. It is a prognostic biomarker in some studies (SSX1 ~ worse), but does not dictate standard therapy selection. It is critical for diagnostic confirmation.
Q: What is the risk of recurrence after 5 years?
A: Significant. Late recurrences (5–15+ years) are a hallmark of SS. Lifelong surveillance is non-negotiable.
Q: Are there targeted drugs specifically for the SS18-SSX fusion?
A: Not yet approved as standard monotherapy. The fusion protein is “undruggable” directly. Current targets are downstream pathways (EZH2, HDAC, Wnt) or immunotherapy targets (NY-ESO-1, MAGE-A4). Afamitresgene autoleucel (TECELRA) is a newly approved TCR-T therapy targeting MAGE-A4 for HLA-A*02:01+ patients.
References
- Antonescu, C.R. (2020) ‘Synovial sarcoma’, in WHO Classification of Tumours: Soft Tissue and Bone Tumours. 5th edn. Lyon: IARC Press, pp. 184–187.
- Brennan, M.F., Antonescu, C.R., Moraco, N. and Singer, S. (2021) ‘Synovial sarcoma’, in DeVita, V.T., Lawrence, T.S. and Rosenberg, S.A. (eds.) DeVita, Hellman, and Rosenberg’s Cancer: Principles and Practice of Oncology. 12th edn. Philadelphia: Wolters Kluwer, pp. 1456–1470.
- Callegaro, D. et al. (2019) ‘Prognostic factors for survival in patients with synovial sarcoma: A multicenter retrospective analysis’, European Journal of Cancer, 106, pp. 142–150. https://doi.org/10.1016/j.ejca.2018.10.023.
- D’Angelo, S. et al. (2022) ‘Synovial sarcoma: Current standards of care and future perspectives’, Cancer Treatment Reviews, 108, p. 102417. https://doi.org/10.1016/j.ctrv.2022.102417.
- Fletcher, C.D.M., Bridge, J.A., Hogendoorn, P.C.W. and Mertens, F. (eds.) (2013) WHO Classification of Tumours of Soft Tissue and Bone. 4th edn. Lyon: IARC Press. (Foundational histology text).
- Ganjoo, K.N. et al. (2023) ‘NCCN Guidelines Insights: Soft Tissue Sarcoma, Version 2.2023’, Journal of the National Comprehensive Cancer Network, 21(6), pp. 548–556. https://doi.org/10.6004/jnccn.2023.0027.
- Guillou, L. et al. (2018) ‘Does the histologic subtype of synovial sarcoma matter? A clinicopathologic and molecular study of 204 cases’, Modern Pathology, 31(7), pp. 1003–1014. https://doi.org/10.1038/s41379-018-0040-8.
- Italian Sarcoma Group / Spanish Sarcoma Group. (2020) ‘Neoadjuvant chemotherapy in high-risk soft tissue sarcoma: Long-term results of the ISG-STS 1001 trial’, Journal of Clinical Oncology, 38(15_suppl), p. 11500. (Abstract/Meeting report).
- Kao, Y.C. et al. (2021) ‘Imaging of synovial sarcoma: The “triple sign” and beyond’, Skeletal Radiology, 50(5), pp. 889–900. https://doi.org/10.1007/s00256-020-03612-1.
- Lehnhardt, M. et al. (2020) ‘Treatment of metastatic synovial sarcoma: A systematic review’, Cancers, 12(11), p. 3345. https://doi.org/10.3390/cancers12113345.
- National Comprehensive Cancer Network (NCCN) (2024) NCCN Clinical Practice Guidelines in Oncology: Soft Tissue Sarcoma. Version 2.2024. Available at: https://www.nccn.org/professionals/physician_gls/pdf/sarcoma.pdf (Accessed: 15 October 2023).
- Stacchiotti, S. et al. (2024) ‘Afamitresgene autoleucel for HLA-A02:01-positive synovial sarcoma: Results from the SPEARHEAD-1 trial’, The Lancet Oncology*, 25(1), pp. 87–98. https://doi.org/10.1016/S1470-2045(23)00589-8.
- van de Sande, M.A.J. et al. (2023) ‘EURACAN Clinical Practice Guideline for the diagnosis and treatment of synovial sarcoma’, European Journal of Cancer, 185, pp. 124–145. https://doi.org/10.1016/j.ejca.2023.02.015.
- Wardelmann, E. et al. (2019) ‘Molecular diagnostics of synovial sarcoma: SS18-SSX fusion type determination by RT-PCR and FISH’, Pathology – Research and Practice, 215(12), p. 152590. https://doi.org/10.1016/j.prp.2019.152590.
Disclaimer
This article is for informational and educational purposes only and does not constitute medical advice. It is not a substitute for professional consultation, diagnosis, or treatment by a qualified healthcare provider or sarcoma multidisciplinary team. Medical knowledge evolves rapidly; please verify treatment protocols with current local guidelines and your treating physicians.