Intrapulmonary solitary fibrous tumor diagnosed by immunohistochemical and genetic approaches: report of a case.

Although solitary fibrous tumors (SFTs) of the pleura are not uncommon, intrapulmonary SFTs are extremely rare. A 72-year-old woman was admitted to our hospital for an investigation of an enlarging intrapulmonary tumor. Because a definitive diagnosis could not be readily established, a pulmonary wedge resection under video-assisted thoracic surgery was performed. Grossly, the tumor was white, well circumscribed, and separate from the pleural surface. Histologically, it consisted of spindle cells proliferating in a vague fascicular pattern, with many dilated capillaries, and intermingled glandular components. These findings suggested a differential diagnosis that included SFT and nonchondromatous pulmonary hamartoma. On immunohistochemical analysis, the spindle cells showed a strong positive reaction to the CD34 antigen. Interphase fluorescent in situ hybridization revealed an absence of HMGA-1 and -2 translocations. These results supported a diagnosis of SFT. A genetic approach may therefore be useful in the differentiation of SFT from nonchondromatous hamartoma.