Case report of primary synovial sarcoma of the thyroid gland: An unusual histology at atypical location

R Lekshmi; Sweety Gupta; Shreeya Pabi; Shreyosi Mandal; Ashok Singh; SP Agarwal; Manoj Gupta

doi:10.4103/jiaps.jiaps_158_22

Journal of Indian Association of Pediatric Surgeons

Official journal of the Indian Association of Pediatric Surgeons

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CASE REPORT

Year : 2023 \| Volume : 28 \| Issue : 2 \| Page : 173-176

Case report of primary synovial sarcoma of the thyroid gland: An unusual histology at atypical location

R Lekshmi¹, Sweety Gupta¹, Shreeya Pabi¹, Shreyosi Mandal¹, Ashok Singh², SP Agarwal³, Manoj Gupta¹
¹ Department of Radiation Oncology, AIIMS, Rishikesh, Uttarakhand, India
² Department of Pathology, AIIMS, Rishikesh, Uttarakhand, India
³ Department of Head and Neck Oncology, AIIMS, Rishikesh, Uttarakhand, India

Date of Submission	30-Oct-2022
Date of Decision	12-Dec-2022
Date of Acceptance	18-Dec-2022
Date of Web Publication	03-Mar-2023

Correspondence Address:
Sweety Gupta
Department of Radiation Oncology, AIIMS, 6^th Level, Medical College Block, Rishikesh, Uttarakhand
India

Source of Support: None, Conflict of Interest: None

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DOI: 10.4103/jiaps.jiaps_158_22

Abstract

Primary synovial sarcoma of the thyroid gland is extremely rare, aggressive, and has a dismal prognosis. We report the case of a 15-year-old male who presented with a progressively increasing neck mass, which was excised and the histopathological and immunohistochemical study suggested biphasic synovial sarcoma of the thyroid gland which was confirmed by synovial sarcoma translocation. There are 14 cases of primary synovial sarcoma of the thyroid reported in the literature so far. This study aimed to document the occurrence of synovial sarcoma histology at an unusual anatomical location with a review of the literature on this rare entity.

Keywords: Immunohistochemistry, surgery, synovial sarcoma, thyroid gland

How to cite this article:
Lekshmi R, Gupta S, Pabi S, Mandal S, Singh A, Agarwal S P, Gupta M. Case report of primary synovial sarcoma of the thyroid gland: An unusual histology at atypical location. J Indian Assoc Pediatr Surg 2023;28:173-6

How to cite this URL:
Lekshmi R, Gupta S, Pabi S, Mandal S, Singh A, Agarwal S P, Gupta M. Case report of primary synovial sarcoma of the thyroid gland: An unusual histology at atypical location. J Indian Assoc Pediatr Surg [serial online] 2023 [cited 2023 Mar 29];28:173-6. Available from: https://www.jiaps.com/text.asp?2023/28/2/173/371167

Introduction

Synovial sarcoma is a mesenchymal neoplasm with some features of epithelial differentiation. It constitutes 5%–10% of all soft-tissue sarcomas with a higher incidence in the third decade and 30% of cases occurring in patients <20 years of age.^[1] Head-and-neck synovial sarcoma is also very uncommon and accounts for 5% of all cases.

The median age at diagnosis is 35 years with 17% of cases occurring in children and young adults.^[2] Primary thyroid synovial sarcoma is rare and the diagnosis and treatment become difficult when tumors arise from uncommon anatomic sites. We here discuss the occurrence of primary synovial sarcoma histology at an unusual anatomical location with its management and review of the literature.

Case Report

A 14-year-old male presented to the outpatient department of our hospital with complaints of an anterior neck mass for 2 months. It was initially small in size but gradually increased in size over the next 2 months. It was not associated with pain, difficulty in swallowing, or a change in voice. The swelling moved with deglutition but not with tongue protrusion. There was no similar swelling in the neck or anywhere else on the body. He had no history of any comorbidities. On examination of the neck mass, there was a swelling of approximately 2 cm × 3 cm in size, which was firm, fixed, nontender, and moved with deglutition. Examination of the oral cavity revealed that the mouth opening was adequate and there was no visible or palpable lesion. There were no palpable neck nodes. Ultrasound of the neck showed a large 4 cm × 3 cm × 2 cm heteroechoic lesion on the left lobe of the thyroid gland which was abutting the left thyroid cartilage and carotid vessel. Fine-needle aspiration cytology from the neck swelling displayed a dispersed population of spindle cells against a hemorrhagic background which exhibited minimal anisonucleosis, granular uncondensed chromatin, inconspicuous nucleoli, and scanty-to-moderate cytoplasm – possibilities of spindle cell neoplasm or papillary carcinoma of the thyroid. A radioisotope thyroid scan was done which showed a normal-sized thyroid gland with adequate function. The patient underwent excision of the lump under general anesthesia. Intraoperatively, the lesion was found to be well encapsulated, 4 cm × 3 cm in size, and was attached to the ala of the thyroid cartilage and extending anteriorly to the strap muscles, superiorly to the superior pole of thyroid ala, inferiorly overlying the superior pole of the thyroid gland, laterally abutting the carotid sheath, and medially involving the thyroid cartilage. Histopathology showed oval-to-spindle-shaped tumor cells with scanty-to-moderate cytoplasm, an oval-to-elongated nucleus with coarse chromatin, and 1–2 nucleoli, arranged in fascicles intersecting at places showing highly cellular areas alternating with less cellular and myxoid areas. Tumor cells showed a high nuclear–cytoplasmic ratio and moderate-to-marked nuclear pleomorphism. Necrosis was not seen and brisk mitotic activity was seen [Figure 1]. Tumor was infiltrating surrounding skeletal muscle bundles and was immunopositive for pan-cytokeratin (CK), CK-7, B-cell lymphoma-2 (Bcl-2), and transducin-like enhancer of split-1 (TLE-1) and negative for smooth muscle actin, desmin, carcinoembryonic antigen, CD-117, S-100, CD-99, Stat-6, myogenin, and calcitonin [Figure 2]. Tumor cells showed diffuse nuclear staining with TLE-1 and translocation for synovial sarcoma on fluorescence in situ hybridization (FISH) for 18q11.2 tested positive. Hence, the diagnosis of biphasic synovial sarcoma was made. Postoperatively, a whole-body positron emission tomography computer tomography scan done reported no evidence of metastasis. He was further planned for adjuvant radiation to the postoperative bed followed by chemotherapy. The patient completed radiation therapy and was referred to medical oncology for further adjuvant chemotherapy.

Figure 1: Histopathology of the tumor (a) (H and E, ×40) a highly cellular spindle cell tumor with pushing margins (infiltration) seen in other areas, (b) (H and E, ×100) tumor composed of spindle-shaped cells with large elongated to spindled nuclei arranged in short interlacing fascicles, (c) (H and E, ×200) higher magnification of the tumor, and (d) (H and E, ×400) higher magnification of the tumor

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Figure 2: Immunohistochemistry of excised tumor (a) staining with Bcl-2, (b) focal staining with CK7, (c) focal staining with pan-CK, (d) some the tumor cells stain with SMA indicating myofibroblastic differentiation, (e) no staining seen with CD99, and (f) no staining seen with calcitonin. SMA: Smooth muscle antigen, Bcl-2: B-cell lymphoma 2, CK 7: Cytokeratin-7

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Discussion

Synovial sarcoma is recognized as a biphasic neoplasm and includes both epithelial and uniform spindle cell components.^[3] After the advent of molecular and molecular cytogenetic diagnostic techniques, FISH or reverse transcription-polymerase chain reaction, considerable morphologic and immunohistochemical heterogeneity within this group of neoplasms has been identified. It can be graded according to the mitotic index, percentage of necrosis, and tumor differentiation. It is locally invasive and has the propensity to metastasize, therefore, considered a high-grade sarcoma. Ninety percent of the synovial sarcoma shows t(X; 18) (p11.2;q11.2) translocation, which involves synovial sarcoma 18 (SS18) formerly synovial sarcoma translocation (SYT) gene on chromosome 18 and one of several synovial sarcoma X genes on chromosome X (usually SSX1 or SSX2), resulting in the formation of SS18-SSX fusion oncogenes.^[1] Synovial sarcoma is a pluripotent mesenchymal malignant tumor that comprises 10% of all soft-tissue sarcoma. The most common site is the extremities, but they can also arise in the head and neck, thorax, and abdomen. Histopathologically, it can be classified as monophasic or biphasic. The monophasic variety exhibits a variety of patterns and is hence difficult to diagnose, whereas the biphasic type consists of epithelioid and spindle components. The various differential diagnoses include spindle epithelial tumor with thymus-like differentiation, spindle cell variety of medullary carcinoma, and undifferentiated anaplastic carcinoma.^[4]

Synovial sarcoma stains positively to epithelial markers such as cytokeratin and nonepithelial markers like CD34 are stained negatively. In this case, the tumor stained was immunopositive for pan-CK, CK-7, Bcl-2, and TLE-1. The most accurate diagnostic method is however SYT/SSX fusion transcript detection by FISH.^[5] To the best of our knowledge, 14 cases of primary synovial sarcoma of the thyroid have been reported in the literature. We discuss a few case studies [Table 1].

Table 1: Few case studies of primary synovial sarcoma thyroid reported in the literature

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In the previous studies, most patients were in the adult age group. Furthermore, surgery has been the mainstay of treatment in all the studies and adjuvant treatment as per histopathological findings.

Most of the case studies in the literature have also utilized molecular genetic analysis for the confirmation of the diagnosis of synovial sarcoma. The primary treatment is surgical resection followed by adjuvant radiation or chemoradiation depending on the presence of high-risk histopathologic features. Resection to obtain clear margins is however difficult in head-and-neck tumors due to proximity to vessels and other vital structures. Therefore, a multimodality treatment including surgery, chemotherapy, and radiation is recommended. In this case, due to the close margin, adjuvant radiation was considered.

Conclusion

Primary synovial sarcoma arising from the thyroid is extremely rare and hence diagnosis and treatment are challenging. Immunohistochemistry and FISH testing should be considered an adjunct for the confirmation of histology whenever in a diagnostic dilemma. Surgical treatment provides the best chance of cure and radiation and chemotherapy must be considered on an individualized case-to-case basis.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form, the legal guardian has given his consent for images and other clinical information to be reported in the journal. The guardian understands that names and initials will not be published and due efforts will be made to conceal identity, but anonymity cannot be guaranteed.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

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