Intrapulmonary Solitary Fibrous Tumor Masquerade Sigmoid Adenocarcinoma Metastasis
A 51-year-old Caucasian female was referred to our institution because of an abnormal nodule detected in her right lung. This had at first been detected four months earlier when she underwent an urgent Hartmann procedure due to refractory adenocarcinoma of the sigmoid colon (pT4N1 stage). Due to the urgency of the surgery, the patient was not staged prior to the surgery but was initially staged after the operation. The only pathologic finding in the computed tomography (CT) of the lung was a nodule in the lower right lobe of 2.5 cm at its longest dimension (), and the patient was staged as cT4N1M1. She received 4 cycles of chemotherapy for the sigmoid adenocarcinoma before she was referred to us for excision of what was believed to be a single metastatic nodule. Although the radiologic findings supported a benign tumor, neither positron emission tomography-CT nor any other procedure to attempt to diagnose the nodule was performed due to the patient's willingness to undergo complete removal of the mass even if it were benign. The patient underwent video-assisted thoracoscopic (VATS) wedge excision of the tumor. She had an uneventful postoperative course and was discharged on the 4th postoperative day.\nThe specimen of the resected lung contained a firm intrapulmonary white-colored well-defined mass with dimensions of 2.5×2.3×2.2 cm. Microscopically, the tumor had a "patternless pattern," with proliferation of bland spindle cells in alternating hypocellular and hypercellular areas, accompanied by a collagenous stroma () with branching hemangiopericytoma-like vessels (). The tumor had no evidence of increased mitotic activity (0 to 1 mitoses per 10 high power fields using an Olympus BH-2 microscope, with a 40× field, 0.5 mm diameter, and area of 0.196 mm2), any significant atypia, or necrosis. Immunohistocemically, the tumor cells were positive for vimentin, CD34 (), and Bcl-2. A few cells were also focally and weakly positive for estrogen and progesterone receptors. The index of cellular proliferation with the antibody Ki-67 is low and estimated at <1% of the cellular population. Immunohistochemistry staining of the tumor cells was negative for alfa-smooth muscle actin (SMA), muscle specific actin (HHF-35), h-caldesmon, CD117 (c-kit), S-100 protein, epithelial antigens (wide spectrum cytokeratins [AE1/AE3] and epithelial membrane antigen), and thyroid transcription factor-1. The resection margins were free of disease. One year after the operation, the patient is well, with no evidence of recurrent disease.