AB018. It’s not always olfactory neuroblastoma—sinonasal undifferentiated carcinoma with frontal base and orbital involvement, a rare disease with poor prognosis: a case report

Background: Malignant neoplasms of the paranasal sinuses and nasal cavity are rare, comprising only 3% of all head and neck malignancies. Sinonasal undifferentiated carcinoma is a rare malignancy and an aggressive neoplasm that was clinic-pathologically distinct from other poorly differentiated malignancies of the nasal cavity and sinuses. The lesion is thought to originate from the epithelium, grows rapidly and invades nearby structures, often resulting in bony destruction while rapid progression of symptoms over weeks to months is characteristic.

Case Description: A 75-year-old man initially presented to ophthalmologist due to blurry vision and diplopia for 2 months. There was also progressive right eye swelling and pain for the past 12 months. Further image study revealed a right superomedial orbital mass with frontal/ethmoid sinus and frontal base extension, causing significant right eye gaze limitation, visual loss, ptosis, chemosis and exophthalmos. He was then transferred to neurosurgical clinic for further treatment where combined surgery was advocated to relieve the mass effect and also for pathology proof. Orbital roof/medial wall and frontal skull base were invaded and destroyed by the tumor. A bicoronal craniotomy was performed and extensive tumor removal was achieved except the orbital fossa due to difficult separation from the ocular muscle and optic nerve. Frontal base was reconstructed in a layered fashion to avoid cerebrospinal fluid (CSF) leakage and infection. He was sent to intensive care unit (ICU) for overnight observation where no further neurologic deterioration occurred. Instant orbital pain relief was noted with significantly decreased proptosis and improving visual acuity. Detailed pathological staining and molecular tests revealed a sinonasal undifferentiated carcinoma, adjuvant chemotherapy was arranged, followed by 30 cycles of radiotherapy. Slight disease progression was noted 12 months after the surgery, chemotherapy regimen was adjusted according to clinical response and he is still currently under regular adjuvant treatment.

Conclusions: Sinonasal undifferentiated carcinoma typically carries a poor prognosis despite aggressive medical and surgical treatment, as it always presents at an advanced stage. Different combinations of chemotherapy, radiotherapy, radical surgical resection have been used to improve the outcome yet there is still not a universal treatment strategy. Early diagnosis, prompt treatment, and comprehensive medical care are crucial to achieve the best possible outcome for affected patients.

Keywords: Sinonasal undifferentiated carcinoma; frontal base; orbital; case report