A fibrous walled cyst is present lined by keratinizing squamous epithelium. The cyst wall does not contain skin adnexal structures. There is a lack of mitotic activity and cytological atypia.
Epidermal inclusion cysts (a.k.a epidermoid cysts) represent about 1% of testicular tumors although whether they are neoplasms or not remains a topic of controversy. One study did show loss of heterozygosity for certain chromosomal loci, supporting a neoplastic process (Younger). They are not associated with intratubular germ cell neoplasia (Diekman).
On gross examination epidermoid cysts of the testis are well circumscribed, soft round nodules ranging from 0.5 to 10.5 cm (average approximately 2 cm). A fibrous capsule of variable thickness, enclosing laminated white or yellowish friable debris is seen. Although most are intraparenchymal, involvement of tunica albuginea or epididymis may be encountered. Microscopically, at least a portion of the cyst wall is lined by keratinzing squamous epithelium. Unlike the benign cystic teratoma of testicle, pilosebacous units and other adnexal structures are lacking.
Cysts typically present as a painless testicular enlargement or may be found incidentally. Infrequently there may be pain, and many have a palpable nontender firm testicular mass. Serum germ cell tumor markers are normal. Ultrasound examination shows a well demarcated, complex intraparenchymal lesion with mixed echogenicity, but the U/S findings are not specific enough for definitive diagnosis and, therefore, surgical exploration usually is undertaken (Umar).
Enucleation has been proposed for these lesions if the lesion is able to be confirmed pre-operatively. If the diagnosis is not suspected pre-operatively, then orchiectomy is often performed
Entirely benign and without recurrence.
Younger C, Ulbright TM, Zhang S, et al. Molecular evidence supporting the neoplastic nature of some epidermoid cysts of the testis. Arch Pathol Lab Med 2003;127:858–860.
Umar SA, MacLennan GT. Epidermoid cyst of the testis. J Urol. 2008 Jul;180(1):335.
Dieckmann KP, Loy V. Epidermoid cyst of the testis: a review of clinical and histogenetic considerations. Br J Urol. 1994 Apr;73(4):436-41.