Dermoid cyst (also known as choristoma) is a benign tumor growing out of a embryonic suture line. The tumour consists of normal cells occurring in an abnormal location. It is usually diagnosed in children when it is first visible but it is not uncommon to have adults coming to the clinic to know if it can be removed.
The MRI scan showed a large intraconal well defined mass sitting right next to the optic nerve causing mass effect which in turn was causing diminution of vision. My working differentials going into surgery- based on location and imaging was Cavernous Hemangioma, Fibrous Histiocytoma, Dermoid cyst, Schwannoma among others.