Urogenital Imaging

Epidermoid cyst, testicular

relatively common benign testicular tumour. The tumour consists histologically of cystic cavities which contain desquamated keratinized epithelium and are lined by stratified squamous epithelium. Skin appendages, such as sebaceous glands and hair follicles, do not occur. The following criteria have been defined for the pathological diagnosis of testicular epidermoid cyst:

  • the lesion is within the testicular parenchyma;

  • the cyst contains keratinized debris or amorphous material with cleft-like spaces;

  • the cyst wall consists of fibrous tissue with an inner lining of squamous epithelium;

  • teratomatous elements are not present in either the cyst wall or the adjacent parenchyma; and

  • the cyst wall is discrete and separate from the tunica albuginea.

    Epidermoid cysts present as a painless palpable firm solitary mass. Bilateral epidermoid cysts are very rare. At ultrasound, epidermoid cysts are well circumscribed ovoid lesions with variable echogenicity. The cyst wall may be hypo- or hyperechoic. The cyst content may be anechoic, uniformly hypoechoic or heterogeneously hypoechoic, or consist of concentric rings of hypo- and hyperechogenicity. The latter can give rise to a typical "target" or "onion" appearance. This laminated appearance should suggest the diagnosis. Calcification of the cyst wall or cyst content can occur. MRI also shows them clearly (Fig.1). These lesions may represent a benign monodermal form of teratoma. However, carcinoma in situ is not found in adjacent seminiferous tubules, unlike typical teratoma. They are considered benign tumours which can be safely treated by local excision, with organ preservation.

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    Fig.1

    Coronal T2-weighted MRI section of the scrotum, showing an epidermoid cyst (arrow) in the medial aspect of the right testis.
    Epidermoid cyst, testicular, Fig.1