Testicular epidermoid cysts: a reevaluation

Abstract

Background: Testicular epidermoid cysts (TECs) are rare benign testicular neoplasms. As TECs are rarely associated with germ cell tumours (GCTs), the understanding of biological behaviour and clinical management of TEC is unresolved.

Methods: We retrospectively searched the files of patients treated for testicular neoplasms and germ cell cancer in the time from 2000 to 2017. Those with TEC were subjected to closer review looking to clinical and histological features, and to results from imaging with ultrasonography (US), contrast enhanced sonography (CEUS) and magnetic resonance imaging (MRI).

Results: Among 589 patients undergoing surgery for testicular tumour, nine simple TECs were identified (1.5, 95% confidence intervals 0.53-2.50%). Median age was 26 years. Imaging revealed sharply demarcated roundish lesions with avascular central areas. Eight patients underwent testis-sparing excision with no recurrence ensuing. One had orchiectomy because of large size of the mass. Histologically, TECs consisted of cornifying squamous cell epithelium and no accompanying germ cell neoplasia in situ. Two additional cases (0.3% of all) required orchiectomy because these TECs were associated with ipsilateral GCT.

Conclusions: TEC is usually a benign lesion that can safely be diagnosed with US, CEUS and MRI due to its roundish shape and its avascular centre. Histologically, this TEC corresponds to the prepubertal-type teratoma unrelated to germ cell neoplasia in situ of the 2016 WHO classification. The other subtype of TEC that is associated with invasive GCT represents a teratoma of postpubertal-type. From a clinical point of view it could be easier to differentiate between a "simple TEC" which is benign (prepubertal type) and a "complex TEC" which is malignant because of its association with invasive GCT.

Keywords: Epidermoid cyst; Germ cell tumour; Scrotal sonography; Testicular neoplasm; Testis sparing surgery.

Fig. 1

a Surgical specimen of excised simple testicular epidermoid cyst. Largest diameter of cyst 1.2 cm. Note the sharply demarcated rim of cyst and the yellowish amorphic mass inside. At the external side of the rim small layer of normal testicular tissue (brownish). b B-mode sonography of testis harbouring epidermoid cyst. Note the typical onion ring shape of the cyst core. c, d Contrast enhanced ultrasonography (CEUS) of testis with simple epidermoid cyst. Dual display with B-mode scan (right side of figure) and CEUS imaging (left side of figure). Note the absence of contrast material (air bubbles) in the centre of the cyst, indicating avascular area

Fig. 2

Scrotal MRI of patient with simple testicular epidermoid cyst, 1.5 Tesla MRI, surface coil. a T1 weighted imaging showing cyst with lower signal intensity than testicular parenchyma. b. T2-weighted imaging: typical bull-eye appearance of epidermoid cyst. Note the high signal intensity within cyst core. c and d. T1-weighted imaging with application of gadolinium-based contrast material. Note signal enhancement in testicular parenchyma but not in the cyst core highlighting the avascular area within the cyst

Fig. 3

a Histological section of surgical specimen with excised testicular epidermoid cyst. Note: Cyst lumen (right side of figure) with layers of cornifying squamous epithelium and cell debris. On the right side normal testicular parenchyma. The cyst is surrounded by a capsule of fibrous tissue. Magnification scale at the upper left side. Hematoxylin eosin stain. b Testicular parenchyma with seminiferous tubules. No germ cell neoplasia in situ. of surgical specimen with excised testicular epidermoid cyst, same patient, higher magnification, see scale at the upper left side. Note: Cyst lumen (upper side of picture) with layers of cornifying squamous epithelium and cell debris. Testicular parenchyma with seminiferous tubules. No germ cell neoplasia in situ. Some tubules with spermatogenesis. Haematoxylin eosin stain

Fig. 4

Histological section of complex testicular epidermoid cyst (left side of figure) in close vicinity to well-differentiated neuroendocrine tumor in testicular tissue outside of cyst (right side of figure). 5x magnification, hematoxylin-eosin stain

Fig. 5

a Patient (adult) with complex Testicular epidermoid cyst, scrotal MRI, 1.5 Tesla, surface coil, coronar section, T1 weighted imaging without contrast material: sharply demarcated roundish cystic lesion at the caudal pole of the left testis. b Patient (adult) with complex Testicular epidermoid cyst, scrotal MRI, 1.5 Tesla, surface coil, coronar section, Gadolinium contrast material: roundish intratesticular cyst at the caudal testicular pole. Note the signal enhancement in the rim region of the cyst, no uptake of contrast material in the cyst centre