title: Role of fine needle aspiration cytology in the diagnosis of a rare case of a poorly differentiated synovial sarcoma with "Rhabdoid" features, including treatment implications.
abstract: Synovial sarcoma is a high-grade, soft tissue sarcoma that is relatively chemosensitive. Its exact diagnosis is crucial, including differentiation from its closest diagnostic mimic, ie, Ewing sarcoma, in view of different treatment options, including chemotherapy regimens, for both these tumors. A 15-year-old girl presented with a recurrent soft tissue mass in her right popliteal region, which was diagnosed as Ewing sarcoma, based on positive immunoexpression of MIC2/CD99, Fli1 and negative expression of LCA and desmin. During her metastatic "work-up", a popliteal lymph node was identified, which was aspirated and examined. Fine needle aspiration cytology smears showed singly scattered and loose, cohesive clusters of cells containing round to polygonal, to short spindle-shaped nuclei with prominent nuclei, and moderate to abundant cytoplasm, including several "rhabdoid" cells. These features prompted a review of the biopsy of the recurrent tumor, and additional immunohistochemical stains, which revealed positive co-expression of pan cytokeratin (AE1/AE3), epithelial membrane antigen (EMA), along with a characteristic variable staining pattern of INI11/SMARCB1. Subsequently, by fluorescent in situ hybridization (FISH) technique, performed on the paraffin section of the recurrent tumor, 100% tumor nuclei displayed SS18 rearrangement, while none of the tumor cells displayed EWSR1 rearrangement. Diagnosis of poorly differentiated SS with "rhabdoid" features was confirmed. This constitutes as the first case, describing cytopathologic features of a poorly differentiated SS with "rhabdoid" features, initially misdiagnosed as a Ewing sarcoma, on biopsy and confirmed as SS by FISH technique. The diagnostic and treatment implications in this case are discussed herewith. Diagn. Cytopathol. 2017;45:662-667. © 2017 Wiley Periodicals, Inc.
authors.affiliation: Department of Surgical Pathology, Tata Memorial Hospital, Mumbai, Maharashtra, India.|Department of Molecular Pathology and Translational Medicine, Tata Memorial Hospital, Mumbai, Maharashtra, India.
authors.forename: Bharat
authors.identifier: http://orcid.org/0000-0002-3509-4794
authors.initials: B
authors.lastname: Rekhi
authors.affiliation: Department of Molecular Pathology and Translational Medicine, Tata Memorial Hospital, Mumbai, Maharashtra, India.
authors.forename: Omshree
authors.initials: O
authors.lastname: Shetty
authors.affiliation: Department of Surgical Pathology, Tata Memorial Hospital, Mumbai, Maharashtra, India.|Department of Molecular Pathology and Translational Medicine, Tata Memorial Hospital, Mumbai, Maharashtra, India.
authors.forename: Mukta
authors.initials: M
authors.lastname: Ramadwar
authors.affiliation: Department of Nuclear Medicine and Molecular Imaging, Tata Memorial Hospital, Mumbai, Maharashtra, India.
authors.forename: Venkatesh
authors.initials: V
authors.lastname: Rangarajan
authors.affiliation: Department of Medical Oncology, Tata Memorial Hospital, Mumbai, Maharashtra, India.
authors.forename: Jyoti
authors.initials: J
authors.lastname: Bajpai
mesh_terms: D000293:Adolescent; D016564:Amyloid beta-Protein Precursor / Q000235:genetics; D014408:Biomarkers, Tumor / Q000235:genetics*; D044963:Biopsy, Fine-Needle; D003937:Diagnosis, Differential; D005260:Female; D015870:Gene Expression; D006801:Humans; D017404:In Situ Hybridization, Fluorescence; D017746:Joint Capsule / Q000378:metabolism / Q000473:pathology / Q000601:surgery; D009364:Neoplasm Recurrence, Local / Q000175:diagnosis* / Q000235:genetics / Q000473:pathology / Q000601:surgery; D010446:Peptide Fragments / Q000235:genetics; D051789:Proto-Oncogene Protein c-fli-1 / Q000235:genetics; D018335:Rhabdoid Tumor / Q000175:diagnosis* / Q000235:genetics / Q000473:pathology / Q000601:surgery; D000071796:SMARCB1 Protein / Q000235:genetics; D012512:Sarcoma, Ewing / Q000175:diagnosis* / Q000235:genetics / Q000473:pathology / Q000601:surgery; D013584:Sarcoma, Synovial / Q000175:diagnosis* / Q000235:genetics / Q000473:pathology / Q000601:surgery; D012983:Soft Tissue Neoplasms / Q000175:diagnosis* / Q000235:genetics / Q000473:pathology / Q000601:surgery
chemical_list: D016564:Amyloid beta-Protein Precursor; D014408:Biomarkers, Tumor; C078433:FLI1 protein, human; D010446:Peptide Fragments; D051789:Proto-Oncogene Protein c-fli-1; D000071796:SMARCB1 Protein; C513266:SMARCB1 protein, human; C543304:amyloid beta-protein precursor C-terminal fragment beta, human
keywords: FNAC; SS18 rearrangement; fluorescent in situ hybridization; rhabdoid cells; synovial sarcoma