Adenomatoid Tumour of the Epididymis

Adenomatoid tumour is a benign tumour of mesothelial origin and the commonest tumour of the epididymis, making up about 30% of paratesticular tumours. It occurs mainly in men aged 20 to 50 years.

It presents as a small, firm, painless nodule, usually at the tail of the epididymis. It has no malignant potential.

Pathophysiology. The tumour arises from mesothelial cells of the epididymis, tunica vaginalis or cord, and forms tubular and gland like spaces lined by flat or cuboidal cells in a fibrous stroma.

Immunostains are positive for calretinin, WT1, cytokeratin, D2-40 and vimentin, and negative for CD34, PAX8 and germ cell markers.

Size is usually about 2 cm, with a range of 0.5 to 5 cm. Bilateral disease and involvement of the testis itself are rare.

The importance lies in separating it from malignant paratesticular tumours, so that a benign nodule does not lead to unnecessary orchidectomy.

A firm, smooth, well defined nodule in or next to the epididymis, which does not transilluminate. Most are painless and found by the patient or at examination, and some cause mild discomfort. The testis is separate and normal.

• Scrotal ultrasound: a well defined, homogeneous, iso- to hyperechoic extratesticular nodule with mild to moderate vascularity.
• MRI when ultrasound is equivocal: an intermediate signal mass with mild enhancement.
• AFP, beta-hCG and lactate dehydrogenase, which are normal.
• Histology after excision, or frozen section at exploration when malignancy cannot be excluded.

Differential diagnosis.

• Epididymal cyst or spermatocele
• Sperm granuloma
• Tuberculous or chronic epididymitis
• Papillary cystadenoma (bilateral in von Hippel-Lindau disease)
• Leiomyoma or fibrous pseudotumour
• Lipoma of the cord
• Metastasis, lymphoma or rhabdomyosarcoma

• Typical ultrasound features, normal markers and no symptoms: surveillance with examination and ultrasound at 3 months, then at 6 to 12 months for 1 to 2 years. Counsel the patient that the risk of cancer is very low.
• Surgery for symptoms, growth, diagnostic doubt or patient preference: inguinal exploration with cord control, delivery of the testis, excision of the nodule with a margin, and frozen section. Epididymectomy for lesions that cannot be separated, with preservation of the testis.
• Orchidectomy only when frozen section shows malignancy or the testis is involved.
• Perioperative cefazolin 2 g intravenously (3 g if over 120 kg) as a single dose. Analgesia: paracetamol 1 g every 6 hours (maximum 4 g daily) and ibuprofen 400 mg every 8 hours for 3 to 5 days.
• Fertility: counsel before epididymectomy, especially if bilateral or in a man with oligozoospermia.
• Complications: haematoma, infection, chronic pain and obstruction of the epididymis. Recurrence after complete excision is very rare.

Monitoring. Wound review at 2 weeks. If under surveillance, review clinically and by ultrasound at intervals set by growth, with biopsy or excision for growth.

Referral and escalation. Refer to urology for any paratesticular mass. Urgent referral for a solid, enlarging, hard or irregular mass, or raised markers.