Unilateral proptosis: a rare presentation of metastatic prostate cancer

Prostate adenocarcinomas with metastatic cranial involvement are rare, with signs and symptoms overlapping with those of the primary base of the skull tumour. The diagnosis was made following a biopsy of the suspected lesions that indicated the possibility of a prostatic primary malignancy based on immunohistochemistry using prostate-specific membrane antigen and subsequently confirmed histologically. We report an unusual case of a 52-year-old male who presented with unilateral proptosis and no prior urological history. Cranial, pulmonary, and thoracolumbar spinal metastases were identified with radiological imaging. We describe the diagnostic evaluation and treatment, as well as outline the rare nature of this case of cranial metastasis of prostate cancer.