術前診断に苦慮した鼻腔内孤立性線維性腫瘍例

抄録

Solitary fibrous tumor (SFT) is a rare mesenchymal tumor that is sometimes encountered in the field of otolaryngology. SFT is classified as an ‘intermediate’ (rarely metastasizing) in the 2020 WHO classification of FIBROBLASTIC/MYOFIBROBLASTIC TUMOURS. It has been reported that embolization is required prior to surgery because of the high blood flow in these tumors. In addition, postoperative recurrence has also been reported in cases of pleural primary tumors, underscoring the importance of preoperative diagnosis and careful postoperative observation. In the case reported herein, the patient presented with the chief complaint of a nasal blockage. Examination revealed a mass filling the left nasal cavity, and biopsy revealed an inflammatory polyp. Thus, we encountered a case in which a SFT was diagnosed by histopathological examination after endoscopic removal of the mass without preoperative vascular embolization. The histological image of irregularly arranged spindle-shaped cells are also known to be present in other mesenchymal tumors such as fibrosarcoma, fibroma, and malignant histiocytoma. Positive immunohistochemistry for CD34 is not a specific finding of SFT, but it is a useful marker for differentiation from the above tumors, since CD34 immunostaining is usually negative in these tumors. The Ki67 index was less than 1%, indicating that the tumor was not malignant. The reason why the preoperative diagnosis was unsuccessful was that the histopathological diagnosis of the tumor showed edematous growth, and an adequate specimen containing the neoplastic lesion could not be obtained by outpatient biopsy. Contrast-enhanced MRI showed a poorly enhancing area in the anterior nasal cavity, and the specimen should have been taken from the posterior lesion, which showed more uniform contrast enhancement. We report this case along with a literature review, including cautions needed for biopsy in preoperative diagnosis.