Solitary fibrous tumor of the oral cavity: An uncommon location for a ubiquitous neoplasm

Solitary fibrous tumor is an uncommon soft tissue tumor initially reported in the pleura but recently described in other sites of the body. To date, only 5 examples of oral solitary fibrous tumor have been reported. Here, we describe 2 additional cases of this tumor in the oral cavity. The tumors were composed of small to medium-sized spindle cells with bland cytologic features; these cells were haphazardly arranged in highly cellular sheets or ill-formed fascicles as well as in hypocellular areas with hyalinized blood vessels. Both tumors contained blood vessels with a hemangiopericytomalike appearance and expressed vimentin, CD34, and CD99. One case was also strongly positive for bcI-2. The diagnosis of solitary fibrous tumor may be difficult inasmuch as it shares a number of histologic features with other soft tissue tumors. Awareness of its occurrence in the oral cavity is important so that confusion with other spindle cell neoplasms can be avoided.