Monophasic spindle cell synovial sarcoma of the head and neck: Report of two cases and review of the literature

Abstract

Synovial sarcoma is a malignant tumor of primitive Report of Cases undifferentiated mesenchymal origin comprising up to 10% of all soft tissue sarcomas.’ The classic histopathologic biphasic synovial sarcoma, consisting of two distinct cell types in varying proportions and patterns, is easily recognized. The epithelial component is composed of cuboidal to columnar cells that commonly form duct-like structures, adjacent to fascicles of spindle-shaped cells with oval nuclei and indistinct cytoplasm. Controversy exists in the literature regarding the presence of a monophasic variety of synovial sarcoma, which fails to display epithelial cells and is composed exclusively of broad sheets of spindle cells. Some pathologists are hesitant to confirm the presence of synovial sarcoma when only one cell type, either spindle or epithelial, is present, because the differential diagnosis of histologically similar tumors is extensive. Mackenzie* states that histologic identification of the biphasic pattern is mandatory in the diagnosis of synovial sarcoma. More recently, however, the monophasic synovial sarcoma, consisting solely of spindle cells, has gained more acceptance as a distinct entity, because positive identification can he documented with the use of immunohistochemical tumor markers. The occurrence of a monophasic variety of synovial sarcoma, either spindle cell or epithelial, in the head and neck is extremely rare, there have heen only four cases reported in the literature,3,4 with three representing metastatic lesions (Table 1). This report presents two cases of primary monophasic spindle cell synovial sarcoma of the head and neck. CASE l* A 28-year-old white man presented with a Cmonth history of right submandibular swelling. He had been treated by a general dentist with incision and drainage and oral antibiotics for a presumed odontogenic infection, without resolution of the mass. The patient complained of slight tenderness of the right neck mass, trismus, and decreased tongue mobility, but denied dyspnea or dysphagia. On physical examination, an 8 X g-cm firm, nonmobile, slightly tender, right anterior cervical neck mass was present. There was no lymphadenopathy. The uvula was deviated to the left, with right palatal draping. A computed tomographic (CT) scan was interpreted as a right submandibular abscess with central necrosis (Fig 1). An incisional biopsy performed through a previous incision and drainage site revealed a poorly differentiated malignant tumor with epithelial features. A metastatic work-up, i’ncluding panendoscopy, bone scan, liver function tests, and head and chest CT scans, was negative.