Primary Synovial Sarcoma of the Thyroid Gland: Case Report and Review of the Literature

Abstract

Synovial sarcoma (SVS) of the thyroid gland is exceedingly rare. We report the case of a 55-year-old man with a rapidly growing 7-cm neck mass. Because of suspicion of anaplastic thyroid carcinoma, a total thyroidectomy was planned, without preoperative cytology. During surgery, the tumor ruptured, leading to fragmented and incomplete resection. The morphological and immunohistochemical aspects suggested thyroid SVS, which was confirmed by fluorescent in situ hybridization (SYT gene rearrangement). The patient experienced immediate local relapse in close contact with large vessels and the thyroid cartilage and was referred to our institution. Doxorubicin-ifosfamide chemotherapy led to a minor response that authorized secondary conservative surgery. Because of microscopically incomplete resection, adjuvant radiotherapy was chosen and is ongoing 10 months after initial surgery. The prognosis of thyroid SVS is associated with a high risk for local and metastatic relapses. Pretreatment diagnosis is fundamental and may benefit from molecular analysis. Margin-free monobloc surgical excision is the best chance for cure, but adjuvant chemotherapy and radiotherapy deserve to be discussed.

Primary Synovial Sarcoma of the Thyroid: Challenges in Cytologic Diagnosis and Review of the Literature

“…Although several cases of SS were reported, only 9 were well documented, by histologic and other ancillary methods, to be of thyroid origin [3][4][5][6][7][8][9][10][11]. The other reported cases did not include or illustrate histopathologic and radiologic evidence of the thyroid as the primary site, while in others the thyroid appeared normal or its involvement Table 3.…”

“…PSST, primary synovial sarcoma of the thyroid; CEA, carcinoembryonic antigen; SMA, smooth muscle actin; TTF1, thyroid transcription factor 1; CK, cytokeratin; EMA, epithelial membrane antigen. DOI: 10.1159/000507312 Clinical and pathologic features of well-documented cases of primary SSs of the thyroid in the English literature Features Kikuchi et al [3] Jang et al [4] Ryu et al [5] Ghafouri et al [6] Boudin et al [7] Shi et al [8] Park et al [9] Yadav et al [10] Nicola et al [11] Cytopathology and Histopathology Papanicolaou stained smears were highly cellular, composed of small monotonous neoplastic cells, arranged in 3D branching fragments and whorls similar to the histologic sections, which also showed 2 cell populations ( Fig. 1a-h).…”

“…Almost all SSs reveal a specific chromosomal change [t(X; 18) (p11.2; q11.2)], which results in the expression of a chimeric SYT-SSX gene transcript [2]. Primary SS of the thyroid (PSST) is very rare, with only 9 well-documented cases reported previously [3][4][5][6][7][8][9][10][11]. This article reports the tenth case, with extensive cytologic, histologic, immunohistochemical, and molecular findings; reviews relevant literature; and discusses the differential diagnostic issues (Tables 1-3).…”

Fine needle aspiration of secondary synovial sarcoma of the thyroid gland

“…Only six cases of primary thyroid SS have been reported . Three were sampled by FNA and all were misdiagnosed as primary thyroid neoplasms, including two medullary carcinomas and one follicular neoplasm . There is only one other report of secondary thyroid SS.…”

Morphology Quiz: Cytopathology of a thyroid neoplasm

“…The predominant group is composed of small to medium, spindle‐shaped cells with ill‐defined cytoplasm, with ovoid nuclei, with fine chromatin and with inconspicuous nucleoli. The second population is very scant and composed of medium to large cells arranged in acinar structures …”