Calcifying synovial sarcoma of the tongue with SS18 rearrangement: a rare variant in a rare location

Synovial sarcoma is a soft tissue malignancy harboring t(X;18) resulting in fusion of two genes SS8 (at 18q11) and SSX (1, 2 or 4 at Xp11) forming the gene fusion product SS18-SSX. It affects adults in their 3rd-4th decades, most frequently in the para-articular regions of the extremities. Less than 10% of the cases occur within the head and neck region and of these, 60% occur in the neck and only 10% occur in the oral cavity. We report a synovial sarcoma of the tongue in a 14-year-old female patient with unusual histology. The patient presented with a mass occupying most of the tongue with extension into the floor of mouth and the lingual gingiva of the anterior mandibular teeth. The tumor was composed of a highly cellular proliferation of spindle cells in a herringbone pattern with many small vessels but without glandular structures, and with extensive calcifications throughout the tumor. Tumor cells were positive for epithelial membrane antigen and transducin-like enhancer of split-1, and fluorescence in situ hybridization studies identified SS18 gene rearrangement. The patient was managed with two debulking procedures followed by chemoradiation and is currently alive with disease. (Oral Surg Oral Med Oral Pathol Oral Radiol 2021;132:e186-e189)