Testicular epidermoid cyst

Testicular epidermoid cysts, also known as keratocysts, are rare benign tumors.

Epidemiology

Testicular epidermoid cysts account for around 1-2% of all testicular masses and typically present in mid-adulthood (2^nd to 4^th decades) ^1,2. They are the most common type of benign testicular neoplasms ⁶.

Clinical presentation

The presentation can be similar to those of malignant germ cell tumors. Patients typically present with a painless and non-tender, testicular mass between 1-3 cm in diameter.

Pathology

Composed of layers of keratinous debris lined with keratinizing squamous epithelium.

Radiographic features

Ultrasound

• non-vascular, well-marginated intratesticular mass
• may demonstrate a characteristic lamellated "onion skin" or "whorled" appearance with alternating hyperechoic and hypoechoic rings
• some lesions may show a target appearance with a halo of hypoechogenicity and a central hyperechoic region

MRI

Tend to be well demarcated.  

• T1: overall signal can be variable; may show alternating rings of high and low signal
• T2: may show a low-intensity rim ³; may also show alternating rings of high and low signal
• T1 C+ (Gd): typically no contrast enhancement ³

Treatment and prognosis

These lesions are benign with no malignant potential ³.

If the diagnosis of an epidermoid is suspected at the preoperative ultrasound, the lesion can be enucleated and frozen sections obtained to confirm the diagnosis. However, treatment is controversial; some authorities advocate orchiectomy, others suggest organ-sparing surgery. 

Differential diagnosis

• testicular germ cell tumor, e.g. seminoma: tends to show vascularity
• testicular teratoma: overlap in appearance ⁷
• tunica albuginea cyst: tends to be completely anechoic
• focal intratesticular granulomatous disease, e.g tuberculosis
• focal testicular hemorrhage