Fine‐needle aspiration of synovial sarcoma: Criteria for diagnosis: Retrospective reexamination of 37 cases, including ancillary diagnostics. A Scandinavian sarcoma group study

Abstract

The cytologic criteria of synovial sarcoma in fine-needle aspirates were defined by a retrospective examination of 37 primary tumors. Irrespective of subtype, a typical pattern at low power was found, provided the yield was rich. The typical pattern was a mixture of dispersed cells with the presence of striped nuclei and cell-tight tumor tissue fragments with irregular borders. Often a branching network of vessels was present in the fragments, imitating a true vascular tumor. Except in poorly differentiated synovial sarcomas, the tumor cells were, small to medium in size, with rounded, ovoid, or fusiform bland nuclei with inconspicuous nucleoli. In the biphasic variant, small glandular- or acinar-like structures were present, although not in all cases. In the poorly differentiated type, however, the cellular pleomorphism was marked with the presence of cells with irregular nuclei and rhabdomyoblast-like cells, corresponding to the pleomorphic variant. The Ewing's sarcoma-like and the atypical spindle cell variants of poorly differentiated synovial sarcoma were not diagnosed in the material. An unequivocal diagnosis of sarcoma is possible when the yield is rich. However, ancillary diagnostics are necessary for a correct diagnosis, to avoid important pitfalls, such as other sarcomas with bland tumor cells and vessel-rich tumor fragments, in particular, solitary fibrous tumor and true hemangiopericytoma. Electron microscopic and/or molecular genetic analyses were better diagnostic adjuncts than immunocytochemistry.

Synovial sarcoma: Diagnosis on fine‐needle aspiration by morphology and molecular analysis

“…The association of these tumors with the characteristic t(X;18) translocation led to the development of molecular genetic techniques, such as RT-PCR and fluorescence in situ hybridization. The applicability of RT-PCR on FNA was demonstrated initially by Nilsson et al, 12 followed by Å kerman et al 16 This made it possible to render an accurate diagnosis on FNA, thereby obviating the need for an open biopsy or core biopsy. In the present study, we successfully performed RT-PCR prospectively from FNA cytology specimen and demonstrated the SYT-SSX fusion transcript in 6 cases, thereby confirming the diagnosis of SS.…”

“…14,15 More recently, Å kerman et al from Sweden 16 have described the cytology of 37 cases, 5 of which had molecular genetic confirmation. The cytology of monophasic SS was described by Ewing et al in 17 cases, 4 of which had molecular genetic analyses on the surgical specimen.…”

“…The morphological features highlighted in our study are in concert with the previous studies quoted. [13][14][15][16][17] The cell yield is usually good and, hence, smears are very cellular. The architectural feature usually evident at low magnification is the prominent pericapillary arrangement, which has been highlighted previously.…”

“…The architectural feature usually evident at low magnification is the prominent pericapillary arrangement, which has been highlighted previously. 16 Typically, the cells of SS are round to oval with a variable admixture of spindle shaped cells, though some cases had the latter predominant cell type. The chromatin in all except 1 case was finely dispersed homogeneous chromatin with inconspicuous nucleoli.…”

“…16,17 In the present study, we describe a detailed analysis of the FNA cytology of 16 cases of SS. In 6 of these cases, RT-PCR carried out on the sample obtained by FNA demonstrated the SYT-SSX fusion transcript, which was further confirmed by DNA sequencing.…”