A clinicopathologic study on SS18 fusion positive head and neck synovial sarcomas

To determine clinicopathologic factors on survival in patients with head and neck synovial sarcoma.

We retrospectively identified patients with molecularly confirmed synovial sarcomas of the head and neck (SS-HN), either by the presence of SS18-SSX fusion transcript by RT-PCR or SS18 gene rearrangement by FISH, who were managed at our institution over a 20-year period (1996-2015). Kaplan-Meier survival analysis and log-rank test were performed to evaluate variables related to disease specific survival (DSS). Fisher exact test was performed to evaluate variables related to local recurrence.

Thirty-four patients (20 males and 14 females, mean of 31years) with SS18-SSX fusion-positive SS-HN were identified. The parapharyngeal region of the neck was the most common site. The mean tumor size was 4.8cm (0.8-10cm). Two-thirds (n=23) of cases had a monophasic histology. The 2, 5 and 10-year DSS rates were 97%, 79% and 68%. The 5-year DSS rates for the adult/pediatric cohort were 74%/88%. Recurrence showed significant effect on DSS (p=0.021). There was no significant effect on DSS with age, therapy modality, tumor site, surgical margin, tumor size (⩽5cm vs. >5cm) and histopathologic subtype. Tumor site (i.e. skull base/paranasal sinus region) was associated with local recurrence (p=0.003).

In our cohort DSS rate was associated with recurrence. Tumors located in the skull base/paranasal sinus region were associated with a higher rate of local recurrence. Thus appropriate selection of high risk patients who can benefit from multimodality therapies might improve survival.