Head and Neck Solitary Fibrous Tumor Presenting as Salivary Gland Tumor: Two Case Reports and Review of the Literature

Abstract

Solitary fibrous tumors (SFTs) are soft tumors (mesenchymal origin) that most likely develop from adult mesenchymal stem cells. SFTs are not common in the head and neck region, and the characteristics of tumors in this location are unclear. The present study describes the clinicopathological findings of 2 cases of SFTs arising in the parotid gland and buccal space, presenting as salivary gland tumors. The first case is a 76-year-old man presenting with a painless tumor on the right parotid gland who subsequently underwent partial superficial parotidectomy. According to the results of histopathological analysis, the tumor consisted of stellate and spindle-shaped cells proliferating on a mucous-like substrate. Immunohistochemical staining revealed that neoplastic cells were positive for CD34, vimentin, Bcl2, and STAT6. The second case is of a 64-year-old man presenting with a painless lump on his right cheek. Based on the findings of fine needle aspiration cytology, a tumor derived from myoepithelial cells of the minor salivary gland or a nonepithelial tumor was suspected. The patient underwent surgical resection via an intraoral approach. Histopathologically, the tumor consisted of spindle-shaped cells with rod-shaped or irregular nuclei. Immunohistochemical staining revealed that the neoplastic cells were positive for CD34, CD99, Bcl2, and STAT6. Briefly, SFT should be considered in the differential diagnosis of a well-marginalized lesion in the salivary gland and oral cavity. STAT6 immunohistochemistry is the most specific and sensitive method of diagnosing SFT. A thorough understanding of the morphological changes associated with SFT and their correlation with clinical, immunohistochemical, and molecular characteristics is important to avoid misdiagnosis.

Keywords: Buccal space; Head and neck; Parotid gland; STAT6; Solitary fibrous tumor.