title: Poorly differentiated synovial sarcoma: immunohistochemical distinction from primitive neuroectodermal tumors and high-grade malignant peripheral nerve sheath tumors.
abstract: Synovial sarcoma is a relatively common sarcoma in adults, which in its classic bimorphic form infrequently poses a diagnostic problem. Monomorphic spindled variants, as well as the less common poorly differentiated variants, may be confused with other soft-tissue sarcomas; the poorly differentiated variant (PDSS), in particular, may be histologically indistinguishable from other small, blue, round cell tumors, including primitive neuroectodermal tumors (PNETs). Detection of the synovial sarcoma-associated t(X;18) by either cytogenetic or molecular genetic approaches may be necessary to confirm the diagnosis of synovial sarcoma in difficult cases. We evaluated 10 cases of PDSS from eight patients using a panel of antibodies (including those to intermediate filament proteins, nerve-sheath associated markers, and neuronal and neuroectodermal associated markers) in order to better establish the immunophenotype of this tumor and to help distinguish it from the tumors with which it may be confused, particularly PNETs and high-grade malignant peripheral nerve sheath tumors (MPNSTs). Our results showed PDSS to have significant immunophenotypic overlap with both PNETs and MPNSTs. In most instances these three entities may be differentiated by a panel of antibodies that should include those to both low and high molecular weight cytokeratins, epithelial membrane antigen, type IV collagen, CD99, CD56, and S-100 protein. Our results also suggest that synovial sarcoma may be a tumor showing combined neuroectodermal and nerve sheath differentiation--perhaps because of translocation-associated expression of specific proteins--rather than a carcinosarcoma of soft tissues or a tumor of specialized arthrogenous mesenchyme.
authors.affiliation: Department of Pathology, University of Washington Medical Center, Seattle 98195, USA.
authors.forename: A L
authors.initials: AL
authors.lastname: Folpe
authors.forename: R A
authors.initials: RA
authors.lastname: Schmidt
authors.forename: D
authors.initials: D
authors.lastname: Chapman
authors.forename: A M
authors.initials: AM
authors.lastname: Gown
mesh_terms: D000071443:12E7 Antigen; D000293:Adolescent; D000328:Adult; D015703:Antigens, CD / Q000378:metabolism; D014408:Biomarkers, Tumor / Q000378:metabolism*; D015815:Cell Adhesion Molecules / Q000378:metabolism; D002648:Child; D003094:Collagen / Q000378:metabolism; D003937:Diagnosis, Differential; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D007621:Karyotyping; D007633:Keratins / Q000378:metabolism; D008297:Male; D008875:Middle Aged; D018396:Mucin-1 / Q000378:metabolism; D018317:Nerve Sheath Neoplasms / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D018242:Neuroectodermal Tumors, Primitive / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D016900:Neurofilament Proteins / Q000378:metabolism; D010524:Peripheral Nervous System Neoplasms / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D013584:Sarcoma, Synovial / Q000235:genetics / Q000378:metabolism* / Q000473:pathology
chemical_list: D000071443:12E7 Antigen; D015703:Antigens, CD; D014408:Biomarkers, Tumor; C061828:CD99 protein, human; D015815:Cell Adhesion Molecules; D018396:Mucin-1; D016900:Neurofilament Proteins; D007633:Keratins; D003094:Collagen