Exploring Clinicopathological and Immunomorphologic Profile of Primary Head Neck Synovial Sarcoma Cases from a Tertiary Care Cancer Centre in India

Abstract Synovial sarcoma (SS) is a malignant mesenchymal neoplasm with variable epithelial differentiation, with a propensity to occur in young adults. The pathognomonic t(X;18) chromosomal translocation and subsequent development of the SS18:SSX fusion oncogenes are the driver of the distinct genomic features. It most frequently occurs in extremities, followed by the trunk, and least common in the head and neck region. Head and neck synovial sarcomas constitutes less than 0.1% of all head and neck cancers and 5–7% of total SS. To study the Clinicopathological, immunohistochemical and molecular features of SS occurring in Head and neck location. A retrospective observational study was conducted over a period of 4 years at a tertiary cancer center after approval of Institution ethical committee. A total of 10 patients diagnosed as SS in head and neck region were included in the study based on exclusion and inclusion criteria. The median age of patients was 24.5 years and mean tumor diameter was 5.6 cm. Sites affected were temporal region, supraglottis, epiglottis, orbit, occipital region, preauricular region, tonsillar region, parapharynx and parotid gland. 2 patients underwent surgery along with adjuvant chemotherapy and radiotherapy and 6 patients received adjuvant chemotherapy or radiotherapy. 6 cases were reported as monophasic SS, 3 as biphasic and 1 as poorly differentiated SS. The most consistent immunohistochemical markers for diagnosis and exclusion of close differentials were TLE-1, SSX-SS18, EMA, CD56, BCL2, and CD99. Molecular diagnostic confirmation was attained only in 1 case. On median follow-up of 6 months, the 2-year disease-free survival rate of the cohort was 47.4 ± 22.8%. Head & neck sarcomas are rare. Meticulous pathologic evaluation and awareness of the typical and atypical histology of SS along with the apt application of immunohistochemical marker such as TLE1 & SS18 and/or cytogenetics (SYT translocation) assist in precise recognition of this entity. The main therapeutic modality is chemotherapy followed by surgery based on patient and tumour characteristics.