SINONASAL SPINDLE CELL CARCINOMA ARISING FROM INVERTED PAPILLOMA IN A PATIENT WITH HISTORY OF RADIOTHERAPY FOR SINONASAL SQUAMOUS CELL CARCINOMA

Carcinosarcoma or carcinoma with spindle cell/sarcomatoid features of the nasal cavity and paranasal sinuses is an exceedingly rare malignancy. We report a case of carcinosarcoma with synchronous inverted papilloma developing in the left nasal cavity and maxillary sinus, in a 72-year-old male with a history of radiation therapy for sinonasal squamous cell carcinoma, 30 years ago. The patient's chief complaint was left nasal obstruction. He also reported purulent nasal drainage, impaired sense of smell and occasional epistaxis. CT imaging showed lobular growth of soft tissue narrowing nasopharyngeal airway with extensive palatal erosion. Endoscopic sinonasal surgery was performed to remove the sinonasal mass. Grossly, the tumor had a white fleshy appearance with tumor necrosis. Microscopically, the tumor was composed of pleomorphic epithelial and spindle cells with frequent mitoses and tumor necrosis. Residual inverted papilloma (IP) with high-grade dysplasia, and foci of keratinizing squamous cell carcinoma (SCC) component (2%) was present at the edge of the main tumor. A transition of SCC to spindle cell carcinoma was present confirmed by focal p63 positivity in both components. The pleomorphic sarcomatoid tumor was positive for vimentin and negative for P40, CK5/6, AE1/AE3, p16, S-100, CD34, CD31, ERG1, SMA, desmin, Sox10, and myogenin with Ki67 highlighting 70% of tumor cells. A final diagnosis of sinonasal sarcomatoid carcinoma associated with residual transformation from IP to SCC was rendered. Due to rarity of such a case, the prognosis and response of treatment is uncertain. So far, no effective targeted therapy has been reported. The patient is currently being treated with aggressive chemotherapy. To the best of our knowledge, this is only the second case of sinonasal carcinosarcoma arising from inverted papilloma with high-grade dysplasia and transition to sarcomaitoid SCC. Perhaps the previous radiation therapy played a role in the development of the sarcomatoid variant of SCC.