• Usually a deep seated mass present for years around large joints (80% in knee and ankle) in young adults (age 20-40), 60% male; only 10% actually involve the joint
• Represent 10% of adult soft-tissue tumors
• 5 year survival is 50-70%; 10 year survival 40%; recurs locally, 10-15% metastasize to lung and pleura, bone, regional nodes
• Rarely radiation associated (Mod Pathol 2002;15:998)
• Minute (< 1 cm) tumors of hands and feet: 2/3 female, median age 29 years, 2/3 monophasic, 40% have microcalcifications; EMA+, keratin+; have clinically favorable course if completely excised (Am J Surg Pathol 2006;30:721)

• Poor prognostic factors: high histologic grade (based on MIB1 index and necrosis, (Hum Pathol 2001;32:257), SYT-SSX1 vs. SYT-SSX2 gene fusion (Mod Pathol 2000;13:482)

• 15 year old boy with mediastinal mass (Interact Cardiovasc Thorac Surg 2012;15:909)
• 22 year old pregnant woman with thigh tumor, and tumor cells detected in peripheral blood monocytes by nested PCR (Am J Surg Pathol 2001;25:406)
• 23 year old woman with non-healing ulcer over buttock (World J Surg Oncol 2012;10:125)
• 28 year old man with mandibular tumor (J Oral Maxillofac Pathol 2011;15:239)
• 59 year old woman with tumor of median nerve of forearm (Turk Patoloji Derg 2012;28:266)

• Wide local excision plus radiation

• Well circumscribed, firm, gray-pink
• Focal calcifications on Xray
• Rarely within major nerves

14 cm mediastinal mass

Buttock mass

Mandibular region

• Biphasic, monophasic or undifferentiated
• Biphasic have spindle cells resembling synoviocytes and plump epithelial cells forming glands/cords
• Monophasic lack the epithelial cells
• Spindle cells are arranged in plump fascicles with hyalinization and distinct lobulation accompanied by mast cells, occasional osseous or cartilaginous metaplasia, focal whorling
• May have hemangiopericytomatous vascular pattern
• Poorly differentiated histology predicts poor outcome

Low power

High power

Cytokeratin

Vimentin

Forearm lesion

Biphasic vs monophasic

Hand between 2nd and 3rd metacarpus

Supraareolar region of breast

Mandibular region

Buttock mass

Various images

• Cytokeratin 7, 8/18, 19 [both components], AE1/AE3 (70% of monophasic fibrous, 46% of poorly differentiated), EMA (epithelial areas, 100% of monophasic fibrous, 92% of poorly differentiated), CD99 / O13 (Ewings/PNET marker, 90-100% of monophasic fibrous or poorly differentiated), vimentin (spindle cells), CEA, bcl-2 (both components, 90% of monophasic fibrous or poorly differentiated) (Am J Surg Pathol 2002;26:1434)
• Also TLE1 (97%, Am J Surg Pathol 2007;31:240), CD57 (neural marker in 72%), E-cadherin (50%), S100 (30-40%), c-kit (children, Am J Surg Pathol 2002;26:486), nuclear beta-catenin
• Mucin in spindle cell areas, PAS positive in epithelium, reticulin highlights biphasic pattern

• CD34 (94% monophasic fibrous, 100% poorly differentiated), desmin (98% monophasic fibrous, 100% poorly differentiated), myogenin (Am J Surg Pathol 2001;25:1150), h-caldesmon, CD141, WT1, FLI-1
• Note: normal synovium is cytokeratin negative

• Glandular formation of epithelioid tumor cells with sparse luminal microvilli

• t(X;18)(p11.2; q11): SYT-SSX1 genes in 90%; can detect via PCR
• Also t(X;18)(p11.21;q11): SYT-SSX2 fusion genes; variants can be detected by optimizing RT-PC (Mod Pathol 2002;15:679, Hum Pathol 2001;32:105)
• p16INK4A gene deletion in 74% (Am J Clin Pathol 2006;126:866)
• High expression of EZH2 helps to distinguish poorly differentiated synovial sarcoma from monophasic and biphasic subtypes (J Transl Med 2012;10:216)

SYT-SSX, SYT-SSX1, and SYT-SSX2

• Fibrous variant resembles other sarcomas
• Metastatic adenocarcinoma: if primarily epithelial component
• MPNST: usually negative for CK7 and CK19 (Am J Clin Pathol 1999;112:641), negative for SYT-SSX fusion products (Am J Clin Pathol 1999;112:43)

• Heavy stromal calcification, 5 year survival of 84% is better than classic tumor

• Good prognosis: young, distal tumor, < 5 cm, < 15 MF/10 HPF, <50% necrosis, no rhabdoid cells, diploid

This information is intended for physicians and related personnel, who understand that medical information is often imperfect, and must be interpreted in the context of a patient's clinical data using reasonable medical judgment. This website should not be used as a substitute for the advice of a licensed physician.

All information on this website is protected by copyright of PathologyOutlines.com, Inc. Information from third parties may also be protected by copyright. Please contact us at copyrightPathOut@gmail.com with any questions (click here for other contact information).