rare soft tissue tumor, it accounts for up to 5 to 8% of soft tissue sarcomas , the fourth most common type of sarcoma after malignant fibrous histyocytoma, liposarcoma and rhabdomyosarcoma ; the most common pediatric non rhabdomyosarcomatous soft tissue cancer; average incidence : 2,75 per 100000 population based on a canandian study

most prevalent in adolescents and young adults, it occurs primarily in the para-articular regions of the extremities, especially the lower ones; rarely, it is encountered in various areas such as parapharyngeal region, abdominal wall, lung or cardiac tissue, ä

well-defined, apparently unrelated to synovium (cf various rare localisations), it displays characteristics of concurrent epithelial and spindle cell proliferation; several types are recognized : two major ones:

biphasic, with epithelial and spindle cell components in various proportions and

monophasic fibrous type;

monophasic epithelial type is much less common ;

may also present as a poorly differentiated small cell neoplasm; diagnosis may be difficult especially for the two later.
in general, very few problems in diagnosis in the biphasic type, may be not ascertained in some instances even after immunohistochemical examination

complete surgical excision of the primary tumor is actually the basis of the treatment; the optimal treatment approach is to be determined as post operative radiotherapy and adjuvant chemotherapy may permit limb preserving surgery and limit local recurrence and (micro) metastasis disease (lung+++)

a t(X;18)(p11.2;q11.2) is found in almost all synovial sarcomas (8O%) whatsoever the histologic type may be; t(X ;18)(p11.2 ;q11.2) seems to be specific : it is not found in other spindle cell sarcomas, and very rarely detected in other tumors as malignant fibrous histyocytoma or fibrosarcomas

detectable by metaphasic and/or interphasic dual colour fluorescent in situ cytogenetics; hybridization combining centomere X or 18 probes with respectively 18 or X whole chromosome painting or YAC probes

both numerical and structural anomalies are found in 50% of cases, numerical anomalies only in 20% (+7,+8,+12,+21,-3, -11, -14, -22) and structural.anomalies only in 20% (involving chromosomes 1, 3, 11, 12, 15, 17 and 21: tumors may be hypodiploid, pseudodiploid, hyperdiploid or near tetraploid without a common pattern; DNA flow cytometry study revealed poorer prognosis for aneuploid tumors

a few variants have been described, involving chromosomes 1, 3, 15 or 21, ...; masked translocations were identified as t(5 ;18), t(X ;7) without chromosome X or 18 apparent involvement respectively

SS18 (synovial sarcoma translocation, chromosome 18)

18q11.2

3,7 kb mRNA

387 amino acids; glutamin, prolin and glycin rich; three potential SH2 binding domains and one SH3; widely expressed, limited to cartlagenous and nervous tissues in early embryonal development; biological properties still unknown

SSX1 (SSX family member 1)

Xp11.23

1,6 kb mRNA

188 amino acids; 81% homologie for SSX1 and SSX2; Kruppel associated box (KRAB) homology; restricted expression to testis and thyroid; biological properties still unknown

5 prime SYT- 3 prime SSX1/2

substitution of the 8 last amino acids of SYT by 78 amino acids of SSX, with exclusion of KRAB and one SH2 domain