Ovarian-type epithelial tumours of the testis: immunohistochemical and molecular analysis of two serous borderline tumours of the testis

A 46-year-old man presented in the urological clinic with painless heaviness of the left testis. Urological examinations showed an intratesticular mass of approximately 2 cm in diameter. On ultrasonography this mass proved to be cystic and solid. The tumour markers were not increased. Under the assumption of a malignant testicular tumour an inguinal orchiectomy was performed. The macroscopic inspection of the surgical specimen, which consisted of testis and testicular appendages, presented a total weight of 23 g and a size of 5 × 4.5 × 3 cm. The cut surface of the testis showed an intraparenchymal, circumscribed formation of cystic appearance with a diameter of 1.4 cm and whitish color.

A 39-year-old man showed an intratesticular mass of approximately 1.5 cm in diameter on urological examinations. The tumour markers were not increased. Under the assumption of a malignant testicular tumour an inguinal orchiectomy was performed. The surgical specimen, which consisted of testis and testicular appendages, presented a total weight of 30 g and a size of 6 × 4 × 3.5 cm. The cut surface of the testis showed an intraparenchymal, circumscribed tumour of cystic appearance with a diameter of 2 cm.

Microscopic examination of testicular sections confirmed the cystic nature of the lesions, which were lined by a fibrous capsule (Fig. 1a) and contained residues of clear fluid. Intraluminal, irregular papillary structures lined by partially multistratified columnar cells and areas of hobnail cells could be seen. The tumour cells exhibited eosinophilic cytoplasm, the nuclei showed predominantly dense chromatin with prominent nucleoli (Fig. 1b-f). Furthermore, there was mild cytological atypia but no mitoses (Fig. 1g + h). Psammoma bodies could not be detected. Proliferative activity revealed by Ki67 staining was below 5 % in both cases (Fig. 2a). Immunohistochemical examination of the tumour cells displayed expression of pan-cytokeratin AE3 (Fig. 2b), estrogen- and progesterone receptor (Fig. 2c-d), Wilms’ tumor protein (WT1), and PAX8 (Paired box gene 8). The BRAF mutated tumour showed strong cytosolic and membranous positivity for B-Raf. Octamer-binding transcription factor-4 (OCT4), calretinin, thrombomodulin and D2-40 were not expressed. The histological findings supported the diagnosis of a serous borderline tumour. The tumour-free testicular tissue displayed regular tubules with intact spermatogenesis and normal interstitial tissue. A Fallopian tubal metaplasia in the paratesticular epithelial structures or ovarian stroma could not be detected. An overview of the immunohistochemical analysis is listed in Table 1.

DNA was isolated from the formalin-fixed and paraffin embeded tumour tissue with InnuPure-Kit and the InnuPure C16 according to the manufacturer’s protocol (Analytik Jena, Jena, Germany). Mutation analyses of both samples were carried out with pyro-sequencing using the Pyromark Q24 (QIAGEN, Hilden, Germany). For KRAS analysis the therascreen KRAS Pyro Kit CE 24 T and therascreen RAS extension Pyro Kit (both QIAGEN) were used. For BRAF analysis the therascreen BRAF Pyro Kit (QUIAGEN) was used. Sequencing was performed according to manufacturer’s protocol. Mutation analysis of BRAF revealed a BRAF V600E (c.1799 T > A) mutation in one case. BRAF codon 464–469 revealed a wild type. Testing for KRAS mutations in exon 2–4 proved to be of wild type in both tumours (Fig. 2e). The clinicopathologic data and cytogenetic findings are listed in Table 2.

CGH was performed as described previously [5]. Comparative genomic hybridization, which was carried out in only one of the tumours due to a lack of tissue, could not detect any chromosomal aberrations.