Although pathologically these lesions are true cysts, they are filled with cheesy laminated material.
Histogenesis of the epidermoid cyst of the testis is uncertain.
Epidermoid cysts may result from monodermal development of a teratoma, or, alternatively, they may be the result of squamous metaplasia of surface mesothelium.
Epidermoid cysts are composed of keratinizing, stratified, squamous epithelium with a well-defined fibrous wall.
They are one of the few benign intratesticular masses and, unlike mature teratoma, have no malignant potential.
Epidermoid cyst of the testis: a review of clinical and histogenetic considerations.Br J Urol.1994;73(4):436-41.
OBJECTIVE: To review the records of patients with epidermoid cysts and those with germ cell tumours to determine the most appropriate method of treatment. PATIENTS AND METHODS: The records of the patients treated for epidermoid cysts and testicular germ-cell tumours in a period covering 22 years were analysed retrospectively. Nine specimens with an epidermoid cyst were examined by immunohistology for the presence of testicular intraepithelial neoplasia (TIN) (or carcinoma in situ of the testis). RESULTS: Ten patients with a simple epidermoid cyst and 481 patients with testicular germ-cell tumour were treated during the observation period. The relative incidence of epidermoid cysts in relation to the number of patients with testicular germ-cell tumours was 2.1% (95% confidence interval 0.8-3.35%). The mean age of the 10 patients with an epidermoid cyst was 24.1 years. The right testis was affected in seven patients and the left in three. Six of these patients received conservative surgery with excellent cosmetic results. No relapse had occurred after a median observation period of 30 months. Immunohistological staining for placental alkaline phosphatase disclosed the absence of TIN in the parenchyma surrounding the cysts. CONCLUSION: The absence of TIN calls into question the common assumption that an epidermoid cyst constitutes a monodermal teratoma. Two distinct entities of epidermoid cyst are proposed--one occurring in conjunction with a teratoma or a germ cell tumour (a 'complex' or 'mixed' epidermoid cyst) and the other a 'simple' epidermoid cyst without TIN in the adjacent tissue and thus representing a benign neoplasm that is not a teratoma. The absence of TIN near a simple epidermoid cyst justifies testis-sparing surgery.
Testicular epidermoid cyst: orchiectomy or enucleation resection? Urologe A.1996 Jan;35(1):1-5.
Our experience with 18 patients with simple epidermoid cysts of the testis is reported. In each patient the tumour was enucleated completely and two biopsies of the adjacent parenchyma were obtained for exclusion of associated germ cell cancer, scars or carcinoma in situ. There was no evidence of malignancy in any of the biopsy specimens. Preoperative evaluation included physical examination, testicular sonography, and determination of AFP and hCG serum levels. Although epidermoid cyst can be strongly suspected on sonography the ultrasound appearance is not specific, and inguinal testicular exploration was required in these patients. In 1 patient multiple epidermoid cysts of the right testis were associated with an adult teratoma containing embryonal carcinoma and choriocarcinoma of the left testis; no similar case has been described in the literature. On the basis of our results and experience we consider tumour enucleation and biopsy of the adjacent parenchyma to be adequate treatment for benign epidermoid cyst. The world literature concerning organ-sparing surgery in testicular epidermoid cyst is reviewed.