Primary Synovial Sarcoma of the Thyroid Gland: Case Report and Review of the Literature
The patient was a 55-year-old Caucasian male with a personal medical history of high blood pressure and smoking. In December 2012, he underwent a cervicothyroid ultrasonography because of a rapidly growing palpable neck mass for 1 month, associated with dysphagia. Physical examination revealed a 7-cm, firm, macronodular, fixed, dipping thyroid mass. No cervical adenopathy was palpable. The WHO performance status was equal to 0. Ultrasonography revealed a 7-cm mass of the left thyroid lobe which was heterogeneous, hypervascularized, and mixed (solid and liquid). Biological thyroid tests, including serum tumor markers, were normal.\nBecause of suspicion of anaplastic thyroid carcinoma, a total thyroidectomy was planned in February 2013, without any preoperative cytology. Intraoperatively, the right thyroid lobe was hypertrophic, firm, but not nodular. The left lobe was under tension, ovalized, and enlarged (more than 12 cm) and extended from the top of the neck to the superior mediastinum. Its mobilization was difficult and led to capsular rupture and effusion of necrotic, hemorrhagic, and gelatinous liquid. Perioperative pathological analysis of tumor fragments showed a spindle cell proliferation suggesting sarcoma. Thyroidectomy was performed without lymph node dissection. Because of perioperative rupture and tumor fragmentation, the resection was classified as incomplete (R2). The postoperative course was uneventful.\nPathological examination (fig. ) of multiple white-tan tumor fragments (between 2 and 3.5 cm each) revealed a dense cellular proliferation composed of ovoid-shaped to frankly spindle-shaped cells, without overt nuclear atypia, and disposed in a fascicular pattern. The mitotic index was moderate, inferior to 10 mitoses per 10 high-power fields. A rich vasculature was composed of branching vessels with a staghorn or hemangiopericytoma-like pattern. There were large hemorrhagic areas, without actual necrosis. On immunohistochemistry (IHC), tumor cells stained heterogeneously but strongly for epithelial membrane antigen (EMA). They were negative for pan-cytokeratin (AE1-AE3), CD34 (only staining the rich vasculature), desmin, H-caldesmon, PS100, HMB-45, and MDM2 antibodies. The diagnosis of monophasic SVS was suspected, and slides were sent to our expert institution for confirmation. Molecular analysis, performed on formalin-fixed paraffin-embedded tissue by fluorescent in situ hybridization (FISH), showed a SYT gene rearrangement, highly consistent with the diagnosis of a monophasic SVS, fibrous type. The histologic grade was 2 in the FNCLCC system (differentiation 3, mitosis count 1, and necrosis 0).\nThe patient was thus referred to our institution. Only 15 days after surgery, clinical examination detected a local disease evolution with palpation of a 4-cm neck mass, associated with dysphagia and pain. Whole-body computed tomography (CT) scan revealed a 5-cm mass, in contact with the frontal parts of the left primitive carotid artery and internal jugular vein and the thyroid cartilage. No lymphadenopathy or distant metastasis was present. Cervical magnetic resonance imaging (MRI) confirmed a 4.2-cm mass in contact with large vessels and likely invasion of the paralaryngeal fat tissue above the thyroid cartilage (fig. ). Because of immediate postoperative relapse, local extension, and known relative chemosensitivity of SVS, we delivered primary chemotherapy combining doxorubicin and ifosfamide, before possible surgery. After 3 cycles, MRI and CT scan showed tumor size stabilization, with a small volume reduction (4 × 3 × 5.5 vs. 4.5 × 3 × 6 cm), associated with extension of necrosis within the mass (60 vs. 20% before chemotherapy). MRI also showed a decrease in fat invasion and contact with the large vessels, whereas perichondrium invasion of the thyroid cartilage remained stable. Three additional chemotherapy cycles were thus delivered. After the last cycle, MRI and CT scan showed small tumor reduction (4 × 2.5 × 4.5 vs. 4 × 3 × 5.5 cm) with further extension of tumor necrosis and improvement of tumor contact with the internal carotid artery and the internal jugular vein, without a resectability margin relative to the thyroid cartilage (fig. ). Chemotherapy was stopped and the patient was operated on. After discussion with the patient, it was decided to perform conservative surgery, without laryngectomy. Tumor resection was done including resection of the previous cutaneous scar, prelaryngeal muscles, thyroid cartilage perichondrium, superior horn of the thyroid cartilage, and left longer horn of the hyoid bone. An additional resection was performed in the thyroidectomy area with removal of fat and lymph nodes in the upper mediastinum. Ipsilateral cervical lymph node dissection was also performed. During the procedure, the left inferior laryngeal nerve was resected, but all other vascular and nervous elements could be preserved (fig. ). No postoperative complications occurred and the patient was discharged after 5 days. Pathological examination of the operative specimen found a 7-cm monophasic SVS. Unfortunately, the resection margins (left cricothyroid muscle) were microscopically involved by tumor cells. No further mutilating surgery was chosen and treatment was completed with ongoing adjuvant radiotherapy.