Sarcoma monophasic synovial

Another spindle cell tumor that shares immunophe-notypic features with MPNST is monophasic synovial sarcoma (MSS). Roughly 40% of cases of MSS show SlOO staining, and approximately 30% are CD57-positive. " Cytokeratin subset analysis may be useful in difficult cases, because most synovial sarcomas are reactive for CK7 or CK19, or both. " In contrast, MPNSTs typically lack those proteins. CD 10-reactivity also favors a diagnosis of MPNST, whereas TLEl-positivity typifies MSS. 

Smith TA, Machen SK, Fisher C, et al. Usefulness of cytokeratin subsets for distinguishing monophasic synovial sarcoma from malignant peripheral nerve sheath tumor. Am J Clin Pathol. 1999 112 641-648. 

Weidner N, Goldman R, Johnston J. Epithelioid monophasic synovial sarcoma. Ultrastruct Pathol. 1993 17 287-294. 

Few mesenchymal tumors including desmoplastic small round cell tumor, leiomyosarcoma and monophasic synovial sarcoma. 

KER, keratin, detected by a mixture of GAMS.2, MAK-6, and AEl /AE3 EMA, epithelial membrane antigen VIM, vimentin DES, desmin MSA, muscle-specific actin SMA, smooth muscle (alpha isoform) actin GALD, h-caldesmon S-IOOP, S-100 protein OCN, osteocalcin LM, laminin UL, Ulex europaeus I lectin binding FS, fibrosarcoma SGRMS, spindle cell rhabdomyosarcoma LMS, leiomyosarcoma MPNST, malignant peripheral nerve sheath tumor MSS, monophasic spindle cell synovial sarcoma SCAS, spindle cell angiosarcoma KS, Kaposi s sarcoma FOS, fibroblastic osteosarcoma. 

Monophasic spindle cell (so-called fibrous) synovial sarcomas represent one extreme of the morphologic spectrum of those neoplasms. Classic biphasic synovial... 

Given the many clinicopathologic similarities between EPS (especially its proximal variant) and the very rare purely epithelioid synovial sarcoma, it would follow that they are difficult to separate by immunophenotypic analysis. A helpful discriminant between these neoplasms is CD34, which is present in EPS but not in epithelioid synovial sarcoma. Moreover, as cited above, Kato and associates found that nearly all EPS cases were immunoreactive for CA125, whereas synovial sarcomas lacked that marker. As mentioned earlier in this discussion, monophasic spindle-cell synovial sarcoma is consistently reactive for nuclear TLEl protein however, that moiety has not been studied specifically in the monophasic epithelioid variant. 

Miettinen M, Limon J, Niezabitowski A, et al. Patterns of keratin polypeptides in 110 biphasic, monophasic, and poorly-differentiated synovial sarcomas. Virchows Arch. 2000 437 275-283. 

Pelmus M, Guillou L, Hostein I, et al. Monophasic fibrous and poorly differentiated synovial sarcoma Immunohistochemical reassessment of 60 t(X 18)(SYT-SSX)-positive cases. Am J Surg Pathol. 2002 26 1434-1440. 

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