On ultrasound, a testicular epidermoid cyst appears as a heterogeneous intratesticular mass without flow on color Doppler. Echogenic foci with posterior sonic shadowing representing calcifications may be present. The lesion may have a hypoechoic or echogenic rim. These findings are nonspecific and usually resection is carried out. The more specific onion skin appearance of alternating hypo- and hyperechoic layers may be present in some cases.
On MRI, T2-weighted images show a hyperintense mass surrounded by hypointense rim. Low-signal-intensity foci representing calcifications may or may not be present. Contrast enhancement is typically not seen. The typical onion skin or target appearance may be present in some cases.