Report of an intrapulmonary solitary fibrous tumor: fine-needle aspiration cytologic findings, clinicopathological, and immunohistochemical features.

The authors describe a rare case of intrapulmonary solitary fibrous tumor (SFT). Morphologically, the tumor showed a disorganized or "patternless" arrangement of plump to spindle cells in a collagenous stroma. Tumor cells were immunoreactive for vimentin, but not for keratin, carcinoembryonic antigen, epithelial membrane antigen, factor-VIII related antigen, S-100 protein, desmin, and actin. These immunohistochemical findings suggested fibroblastic differentiation, in keeping with the putative submesothelial origin of the tumor. The problems concerning the fine-needle aspiration (FNA) preoperative diagnosis of SFT are briefly discussed.