Epidermoid cyst of the testis.

Epidermoid cysts, though having a variable sonographic appearance, may present with an onion peel configuration, that is, concentric rings of alternating hyperechogenicities and hypoechogenicities. The absence of vascular flow on colour Doppler sonography is also consistent with the avascular nature of these lesions. By combining these two sonographic features and the absence of biochemical tumour marker, preoperative diagnosis of epidermoid cyst is possible and may prompt a testis sparing surgery rather than orchidectomy.