BACKGROUND: Solitary fibrous tumors (SFT) occur mainly in the pleura and other serosal sites. However, they have been found in extraserosal sites and should be considered in the differential diagnosis (DDx) of any spindle cell lesion, including those in the gastrointestinal tract. In this report, we describe fine needle aspiration (FNA) cytologic evaluation of a gastric SFT, emphasizing the role of immunocytochemistry in the DDx. CASE: Computerized tomography-guided FNA of a subserosal gastric mass in a 77-year-old female was performed. The moderately cellular smears showed neoplastic cells arranged in interlacing fascicles and in a "patternless" pattern. There was variable collagenous stroma. The cell block revealed a similar pattern, with a single mitotic figure. Nuclear atypia and necrosis were absent. The neoplastic cells were strongly reactive for vimentin and CD34, with weak focal reactivity for smooth muscle actin, suggestive of vessels in tangential section. They were nonreactive for muscle specific actin, desmin, S-100 and pancytokeratin. Other immunocytochemical markers were also studied. CONCLUSION: SFT should be considered in the DDx of spindle cell lesion of the stomach. Cell block and immunocytochemical markers, especially CD34, were extremely useful in the diagnosis of SFT on FNA.
BACKGROUND: Solitary fibrous tumors (SFT) occur mainly in the pleura and other serosal sites. However, they have been found in extraserosal sites and should be considered in the differential diagnosis (DDx) of any spindle cell lesion, including those in the gastrointestinal tract. In this report, we describe fine needle aspiration (FNA) cytologic evaluation of a gastric SFT, emphasizing the role of immunocytochemistry in the DDx. CASE: Computerized tomography-guided FNA of a subserosal gastric mass in a 77-year-old female was performed. The moderately cellular smears showed neoplastic cells arranged in interlacing fascicles and in a "patternless" pattern. There was variable collagenous stroma. The cell block revealed a similar pattern, with a single mitotic figure. Nuclear atypia and necrosis were absent. The neoplastic cells were strongly reactive for vimentin and CD34, with weak focal reactivity for smooth muscle actin, suggestive of vessels in tangential section. They were nonreactive for muscle specific actin, desmin, S-100 and pancytokeratin. Other immunocytochemical markers were also studied. CONCLUSION: SFT should be considered in the DDx of spindle cell lesion of the stomach. Cell block and immunocytochemical markers, especially CD34, were extremely useful in the diagnosis of SFT on FNA.