Primary Synovial Sarcoma of the Thyroid Gland Presenting With Early Pulmonary Metastasis: Diagnostic Pathway, SS18 Gene Fusion Confirmation, and Clinical Course.
Andrew G Edwards, Jack Petroski, Raj Patel et al.
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Case in brief
A 47-year-old woman presented with dysphagia and a left-sided neck mass. Initial fine-needle aspiration was non-diagnostic; repeat sampling suggested a spindle cell neoplasm. After left hemithyroidectomy with negative margins, SS18 gene fusion on fluorescence in situ hybridization confirmed primary synovial sarcoma of the thyroid. Neck radiation was given, but pulmonary metastasis was detected 6 months after surgery. Despite subsequent systemic therapy, disease progressed to the brain and bones. Doxorubicin treatment was complicated by congestive heart failure, and she died of metastatic disease 65 months after presentation.
What made this case unusual
The thyroid spindle cell tumor was confirmed as synovial sarcoma by SS18 fusion testing after non-diagnostic initial aspiration; pulmonary metastasis developed despite negative-margin resection and neck radiation.
Diagnostic / clinical pearl
When aspiration of a thyroid spindle cell mass is non-diagnostic, SS18 fusion testing by FISH can establish synovial sarcoma and clarify the diagnosis.
Why it matters
The case illustrates that negative margins and neck radiation did not prevent early pulmonary and later systemic metastases, while doxorubicin was complicated by congestive heart failure.