Dermoid Cyst of the Testis

Juan E Small, MD - Case Coordinator
Amy Ho Huang, MD - Radiology Discussion
Xuefei Hong, MD - Pathology Discussion
Koenraad Mortele, MD - Attending Radiologist
Steven E Seltzer, MD - Attending Radiologist
Pablo R Ros, MD, MPH - Attending Radiologist

August 11, 2003

Presentation

Imaging Findings

Axial CT images through the scrotum (acquired two years previously) show a fat-attenuation mass in the right scrotal sac at the expected location of the right testicle. At that time, the patient reported that the mass had been present since childhood and had not increased in size.

Two years later, the patient noticed a painless increase in the size of the right hemiscrotum. Ultrasound images show a mass adjacent to the upper pole of the right testicle with focal calcifications and posterior shadowing. These findings suggest the possibility of a dermoid cyst.

Diagnosis

Discussion

The cyst contains hair and has "cheesy" protrusions. Microscopy of a section of the cyst wall shows a squamous lining with underlying sebaceous glands and hair follicles. The image also shows a focal area of chronic inflammation. This area is composed of giant cells. The mass is adjacent to the rete testis and a small amount of testicular parenchyma.

Radiology Discussion:

Evaluation of a scrotal mass should begin with two questions : 1) is the mass intratesticular vs. extratesticular, and 2) is the mass cystic or solid? Answering these questions helps narrowing the differential diagnosis. In general, extratesticular masses tend to be benign, while intratesticular masses are malignant. In general, cystic lesions, particularly if extratesticular, are less worrisome than solid lesions.

Here is a list of common differential diagnoses:

a) Extratesticular cystic masses (almost universally benign): hydrocele, epididymal cyst.

b) Solid extratesticular masses [generally (97%) benign]: hernia, lipoma (spermatic cord or epididymis), and adenomatoid tumor (epididymis); malignant entities include rhabdomyosarcoma, liposarcoma, and MFH.

c) Intratesticular cystic masses [also typically (>95%) benign]: simple cyst, epidermoid cyst, tunica albuginea cyst. Teratoma is the one possible malignant entity, but generally contains calcifications or some solid elements.

d) Solid intratesticular masses [generally (95%) malignant]: germ cell tumors vs. metastases (from prostate, kidney, lymphoma, leukemia). Note: if the testicular mass is palpable, there is a higher chance of malignancy.

This case represents a mass with shadowing on ultrasound that suggests calcification. Though common in mixed germ cell tumors and teratomas, mineralization is rare in pure seminomas. The diagnosis for this case is a very rare entity called a dermoid cyst of the testicle.

Dermoid cysts are typically palpable, firm, nontender masses. Case reports indicate occurrence over a wide range of ages, from 5-67 years. Unlike teratomas, dermoid cysts are composed entirely of ectodermal derivatives. The cyst is typically well-encapsulated and unilocular, and occurs more often in the right testicle (upper/lower pole). The most commonly reported treatment consists of enucleation and follow up.

References

Ford J, Singh S. Paratesticular dermoid cyst in 6-month old infant. The Journal of Urology 139, January, 1988:89-90.

Kurtz AB, Middleton WD. Ultrasound: The requisites. Mosby, St. Louis, 1996.

Middleton WD. General and Vascular Ultrasound Case Review. Mosby, St. Louis, 2002.

Weissleder R et al. Primer of Diagnostic Imaging, 2nd Ed. Mosby, St. Louis, 1997.

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