Which lesion presents with a well defined hypoechoic mass, thickened or calcified wall, and an 'onion' appearance internally?

Which lesion presents with a well defined hypoechoic mass, thickened or calcified wall, and an 'onion' appearance internally?

• A. Spermatocele
• B. Simple Epididymal Cyst
• C. Epidermoid cyst
• D. Epididymal cyst

Answer: (C)

The key idea is recognizing an epidermoid cyst of the testis by its onion-like internal pattern. This lesion is an intratesticular, well-defined mass that shows laminated concentric rings of keratin, producing an onion-skin or target-like appearance on ultrasound. The wall can be thickened and may contain calcifications from keratin buildup. It is typically avascular on color Doppler, which helps separate it from vascular testicular tumors. In contrast, those options arising from the epididymis (like epididymal or simple epididymal cysts) are outside the testis, usually anechoic or contain debris, and lack the characteristic lamination. Therefore, the described features most fit an epidermoid cyst.

The key idea is recognizing an epidermoid cyst of the testis by its onion-like internal pattern. This lesion is an intratesticular, well-defined mass that shows laminated concentric rings of keratin, producing an onion-skin or target-like appearance on ultrasound. The wall can be thickened and may contain calcifications from keratin buildup. It is typically avascular on color Doppler, which helps separate it from vascular testicular tumors. In contrast, those options arising from the epididymis (like epididymal or simple epididymal cysts) are outside the testis, usually anechoic or contain debris, and lack the characteristic lamination. Therefore, the described features most fit an epidermoid cyst.