[Extrapleural solitary fibrous tumor mimicking lateral neck cyst--a case report].

A 62-year-old man was referred to the Department of Dentistry because of ultrasonographic finding of "cystoid lesion with relationship to right parotid gland". During operation, a tumor mass without any relationship to parotid gland but attached to the right internal carotid artery was found. Grossly, the tumor was well circumscribed, spheric, measuring 40 mm in diameter; it was of solid, firm appearance and tan-to-white color on cross section. Microscopically, the tumor cells were round to spindle-shaped with vesicular nuclei and eosinophilic cytoplasm, arranged in fascicular pattern. Immunohistochemically, the cells expressed vimentin, CD 34, smooth muscle actin, and bcl-2 protein. On the basis of microscopical appearance and results of immunohistochemistry, the diagnosis of solitary fibrous tumor (cellular variant) was established. One year after resection, the patient is free of disease. A new concept of this uncommon mesenchymal tumor is discussed.