Metastatic Prostate Carcinoma Masquerading as Primary Sphenoid Sinus Tumour: A Case Report

Metastasis from prostate adenocarcinoma to Paranasal Sinuses (PNS) is extremely rare. Usually, they metastasise to the pelvic lymph nodes and bones of the axial skeleton. Authors hereby, present a case of a 71-year-old male patient with diplopia on left lateral gaze and frontal headache since two months. On examination, he had left lateral rectus palsy. Computed Tomography (CT) Brain was normal. Computerised Tomography of Paranasal Sinuses (CT PNS) and Magnetic Resonance Imaging (MRI) brain revealed an ill-defined isodense lesion causing clival erosion and extending anteriorly to the sphenoid sinus. The patient underwent endoscopic endonasal trans-sphenoidal excision. The histopathological diagnosis was adenocarcinoma. Immunohistochemistry (IHC) was done for further evaluation which showed both CK7 and CK20 to be negative. Hence, sinonasal carcinoma was excluded and possibility of metastatic tumour was considered. Ultrasonography (USG) abdomen was normal and further IHC showed Prostate-Specific Antigen (PSA) positivity. Elevated serum PSA and Positron Emission Tomography (PET) scan confirmed primary carcinoma prostate with multiple skeletal metastases. The patient was treated with a Gonadotropin-Releasing Hormone (GnRH) antagonist and an antiandrogen which showed good response. So, the possibility of metastasis from an occult primary prostate carcinoma was considered as the differential diagnosis in an elderly patient presenting with sinonasal mass. Hence, proper screening and IHC studies are mandatory for accurate diagnosis and treatment.