Synovial sarcoma, monophasic fibrous and poorly differentiated

Intrathoracic synovial sarcomas show a high proportion that are poorly differentiated.

Immunohistochemistry

The diagnoses in publications^1&4 were proven by the presence of the translocation t(X:18)(p11.2;q11.2).

	monophasic fibrous	poorly differentiated
AE1/AE3	33/471, 0/14	6/131	only one poorly differentiated tumour was negative for all three markers
pancytokeratin KL1	23/471	5/131
EMA	47/471, 1/1 (focal positivity)4	12/131
Cytokeratin 1	5/463
Cytokeratin 5/6	0/243	0/93
Cytokeratin 7	46/713	9/183
Cytokeratin 8 / 18	21/463	8/173
Cytokeratin 10	0/443	0/183
Cytokeratin 13	0/453	0/18
Cytokeratin 14	11/403	1/123
Cytokeratin 19	41/743	11/183
Cytokeratin 20	3/473	0/183
E-cadherin	22/471, 8/82	7/131, 2/22
coexpression of E-cadherin and KL1	10/471	4/131
coexpression of E-cadherin, KL1 and AE1/AE3	8/471	3/131
expression of only one of E-cadherin, KL1 and AE1/AE3	10/471	3/131
expression of at least one of E-cadherin, KL1 and AE1/AE3	47/601
CD34	3/47 : focal positivity1, 1/1 (almost all tumour spindle cells positive)4	0/131
S-100	18/471, 0/14	3/131
SMA	10/471	1/131
h-Caldesmon	0/471	0/131
Desmin	1/471	0/131
bcl-2	43/471	12/131
CD99	43/471	13/131
CD117	5/471	1/131

Cytogenetics

Independent of morphology, more than 90% of all synovial sarcomas show the translocation t(X;18)⁴.

Differential diagnosis

• fibrosarcoma

• leiomyosarcoma

• malignant peripheral nerve sheath tumour

• haemangiopericytoma

• spindle cell carcinoma

• Ewing sarcoma: FISH to demonstrate cytogenetic differences may be useful: t(11;22) in Ewing's sarcoma and t(X;18) in synovial sarcoma.

References

¹Pelmus, M., L. Guillou, et al. (2002). "Monophasic fibrous and poorly differentiated synovial sarcoma: immunohistochemical reassessment of 60 t(X;18)(SYT-SSX)-positive cases." Am J Surg Pathol 26(11): 1434-40.

²Sato, H., T. Hasegawa, et al. (1999). "Expression of E-cadherin in bone and soft tissue sarcomas: a possible role in epithelial differentiation." Hum Pathol 30(11): 1344-9.

³Chu, P. G. and L. M. Weiss (2002). "Keratin expression in human tissues and neoplasms." Histopathology 40(5): 403-39. (Summary data from multiple papers)

⁴Cote, J. F., P. P. de Saint-Maur, et al. (2004). "Unusual strong CD34 positivity in a thoracic monophasic fibrous synovial sarcoma." Histopathology 45(5): 539-40.

This page last revised 12.1.2005.

©SMUHT/PW Bishop