INTRODUCTION

Primary adenocarcinoma of the rete testis was first reported by Feek and Hunter in 1945.¹

It is a very rare diagnosis, with only about 60 reported cases. It tends to be found in the elderly, with its peak incidence in patients 70 years of age.²

To the best of our knowledge, the present report is the first on adenocarcinoma of the rete testis associated with prostate cancer.

CLINCIAL CASE

An 84-year-old man presented with a history of castration-resistant prostate cancer treated with abiraterone acetate and prednisone and a history of urinary retention, with an indwelling catheter.

Physical examination revealed a non-tender, solid, poorly-defined right testicular mass. Neither the testis nor the epididymis could be identified at palpation. Tumor markers were within normal limits (Figure 1). The patient underwent radical orchiectomy and pathologic evaluation was carried out.

Figure 1 Physical evaluation revealing a testicular mass. 

Macroscopic examination of the surgical specimen showed a 9 x 7 x 6-cm whitish, rough, renitent, heterogeneous mass (Figure 2).

Figure 2 Surgical specimen with tumor occupying more than 60% of the testicular parenchyma. 

Histologically, the tumor was a well-defined adenocarcinoma of the rete testis with a biphasic pattern, infiltration of the tunica vaginalis and epididymis, and lymphovascular invasion. Immunohistochemistry staining was positive for high molecular weight cytokeratin (CK HMW) and cytokeratin 5/6, and negative for PSA (Figure 3). After those findings, chemotherapy was offered but it was refused.

Figure 3 Tumor cells filling the glandular spaces and forming papillary protrusions into the lumen, with immunohistochemical staining positive for cytokeratin 5/6, reduced from x400. 

DISCUSSION

Adenocarcinoma of the rete testis is a very rare entity. Upon initial evaluation, patients tend to have sought medical attention for a non-painful testicular mass, and tumor markers are usually negative.³

In some cases, physical examination can evidence an associated inguinal hernia, hydrocele, undescended testis, epididymitis, or hematocele.⁴

Our patient presented with none of those conditions. On the other hand, he had a history of castration-resistant prostate cancer, and to the best of our knowledge, the present report is the first on adenocarcinoma of the rete testis associated with prostate cancer.

Diagnosis is made according to pathologic findings. A few cases have been evaluated using immunohistochemistry and were positive for cytokeratin, epithelial membrane antigen, and carcinoembryonic antigen. However, the immunohistochemistry profile has not been well defined.^5-7

All the criteria for diagnosing primary carcinoma of the rete testis, which have been reported and revised by Nochomovitz and Orenstein, were fulfilled in the current case: absence of histologically similar extra-scrotal tumor that plausibly could be the primary site, tumor centered on the hilum, morphology incompatible with any other type of testicular or paratesticular tumor, and immunohistochemical exclusion of other possibilities.⁸

In our case, metastatic extension from the prostate was excluded due to negative staining for PSA.

Because adenocarcinoma of the rete testis is extremely rare, there is a lack of consensus regarding treatment and follow-up strategies. Consequently, prognosis of those neoplasms is poor, with a 5-year survival rate of 13%.⁹

Different adjuvant therapies have been described: retroperitoneal lymph node dissection, radiotherapy, and chemotherapy; all of them inducing only poor response.¹⁰

Data are scarce regarding treatment and follow-up strategies due to the rarity of the tumor.

Immunohistochemistry could be useful for achieving an accurate diagnosis in such cases.