Inability of PET/CT to identify a primary sinonasal inverted papilloma with squamous cell carcinoma in a patient with a submandibular lymph node metastasis: A case report.

The present study describes the first reported case of a sinonasal inverted papilloma (IP) with squamous cell carcinoma (SCC) that presented as a cancer of unknown primary in the English-language literature. In July 2010, a 66-year old male presented with a 6-month history of a painless, progressive mass in the right submandibular region. Physical examination revealed a 3×4-cm smooth, non-tender mass and subsequently, excision of the right submandibular gland was performed. Post-operative pathological examination indicated poorly-differentiated SCC of the submandibular lymph node. Positron-emission tomography/computed tomography (PET/CT) was unable to identify the primary tumour site in this case, and 14 months later the patient presented with nasal obstruction, leading to the diagnosis of right sinonasal IP with coexistent SCC. The patient received pre-operative radiotherapy, a right total maxillectomy and post-operative radiotherapy. However, the patient succumbed to a distant metastasis 37 months after the initial presentation. 18F-fluorodeoxyglucose uptake on PET/CT may be not a reliable predictor of malignancy in sinonasal IPs. Therefore, we suggest emphasis of the use of multiple biopsies for suspected sinonasal IPs in order to improve diagnostic accuracy.