title: Fine needle aspiration of primary mediastinal synovial sarcoma: cytomorphologic, immunohistochemical, and molecular study.
abstract: The cytologic diagnosis of synovial sarcoma (SS) can be difficult when it occurs in unusual locations, atypical age groups, and/or have unusual morphology. We report a case of primary mediastinal SS in a 65-year-old male with a long smoking history who presented with increasing shortness of breath and was found to have a 14.2 cm mediastinal mass. Smears from the endobronchial ultrasound guided fine needle aspiration of the mass were moderately cellular consisting of loosely cohesive clusters, some of which demonstrated nuclear molding, and dispersed single cells. The relatively uniform tumor cells had a high nuclear-to-cytoplasmic ratio, finely granular chromatin, and inconspicuous nucleoli. Some of the single cells had spindled morphology with unipolar wispy tails and naked nuclei. Based on the clinical presentation and the cytomorphologic features, our initial differential diagnoses included atypical carcinoid, small cell carcinoma, basaloid squamous cell carcinoma, sarcoma, and lymphoma. Immunohistochemical studies on the cell block sections revealed that the tumor cells were focally positive for cytokeratin and diffusely positive for CD56, while negative for CD45, synaptophysin and chromogranin. Ultimately, an immunohistochemical stain for TLE-1 demonstrated diffusely strong nuclear positivity and molecular studies showed the presence of the t(X; 18) SYT/SSX1 translocation confirming the diagnosis of SS. In this report, we describe the cytomorphologic features of SS, its diagnostic pitfalls, and potential mimics in the mediastinum.
authors.affiliation: Department of Pathology, University of Michigan, Ann Arbor, Michigan.
authors.forename: Cheng Cheng
authors.initials: CC
authors.lastname: Huang
authors.forename: Claire W
authors.initials: CW
authors.lastname: Michael
authors.forename: Judy C
authors.initials: JC
authors.lastname: Pang
mesh_terms: D000368:Aged; D014408:Biomarkers, Tumor / Q000032:analysis* / Q000235:genetics*; D044963:Biopsy, Fine-Needle; D019002:CD56 Antigen / Q000032:analysis; D056970:Co-Repressor Proteins; D006801:Humans; D007633:Keratins / Q000032:analysis; D019394:Ki-67 Antigen / Q000032:analysis; D008297:Male; D008479:Mediastinal Neoplasms / Q000737:chemistry* / Q000209:etiology / Q000235:genetics / Q000473:pathology*; D009363:Neoplasm Proteins / Q000235:genetics; D029424:Pulmonary Disease, Chronic Obstructive / Q000209:etiology; D012097:Repressor Proteins / Q000032:analysis / Q000235:genetics; D013584:Sarcoma, Synovial / Q000737:chemistry* / Q000209:etiology / Q000235:genetics / Q000473:pathology*; D012907:Smoking / Q000009:adverse effects; D014178:Translocation, Genetic
chemical_list: D014408:Biomarkers, Tumor; D019002:CD56 Antigen; D056970:Co-Repressor Proteins; D019394:Ki-67 Antigen; D009363:Neoplasm Proteins; D012097:Repressor Proteins; C499043:TLE1 protein, human; C093962:synovial sarcoma X breakpoint proteins; D007633:Keratins
keywords: cytology; fine needle aspiration; mediastinum; synovial sarcoma