the primary complaint of most patients with this tumor is testicular swelling , which is usually painless . it is not uncommon for this tumor to be of an advanced stage at the time of the diagnosis , and the prognosis is dismal . although scrotal swelling is the most common manifestation , the clinical presentation is often nonspecific and may not suggest a neoplasm , such that the diagnosis can be delayed . to our knowledge , this is the first report in the published literature documenting incidental adenocarcinoma of the rete testis with preceding detection of unilateral hydronephrosis . the patient was a 54-year - old man with right flank pain that had started 1 month previously . the kidney - ureter - bladder and urinalysis findings were normal , but ultrasonography showed mild right hydronephrosis . therefore , abdominopelvic computed tomography ( ct ) was performed to determine the cause of the hydronephrosis . we found multiple enhanced lesions around the right obturator muscle that were compressing the right distal ureter and causing the hydronephrosis . additionally , a heterogeneous , low - density lesion with an irregular margin was found with hydrocele in the right testis ( fig . according to the patient 's medical history , the painless swelling of the right scrotum had started about 1 year previously with no other significant medical history . on the physical examination , a relatively movable iu / l ) and carcinoembryonic antigen ( cea , 40.8 ng / ml ) levels were higher than normal , but the alpha - fetoprotein and beta - human chorionic gonadotropin ( beta - hcg ) levels were normal . we decided to perform cystoscopy and retrograde pyelography with radical orchiectomy to rule out any metastatic lesions in the right ureter . a right ureteral stricture was found and a d - j ureteral catheter was inserted . microscopic examination showed conventional adenocarcinoma , which shows a glandular pattern of growth with atypical stratified cuboidal to columnar epithelial tumor cells ( fig . significant immunohistochemical reactivities for cea , muc1 , cytokeratin 20 , and cdx2 were seen ( fig . there was no reactivity for prostate - specific antigen ( psa ) , carbohydrate antigen 19 - 9 , thyroid transcription factor-1 , or s-100 protein . positron emission tomography - ct ( pet - ct ) , gastroduodenoscopy , colonoscopy , and transrectal ultrasound were performed in addition to measuring the serum psa level to rule out metastatic adenocarcinoma from another site . , we finally diagnosed a right testicular lesion as the primary adenocarcinoma in the rete testis . after the radical orchiectomy , the patient received combined chemotherapy 6 times , but the progression of the disease was unstoppable . during the course of the chemotherapy , pet - ct was done , which revealed newly developed lung metastasis . up to one quarter of these tumors have been reported in association with scrotal hydrocele , as in our case . the diagnosis is often difficult and made incidentally   and is often delayed , because of the nonspecific clinical presentation , which can suggest only an inflammatory process . the time from the initial problem to presentation averages approximately 24 months . in an extensive review of reported cases , 54% of patients had metastases at diagnosis with lymphatic spread to the lumboaortic and iliac nodes and metastases to the bones , lungs , and skin . the common sites of early metastases are the lymph nodes , lungs , liver , and bones . the diagnostic criteria of nochomovitz and orenstein   for adenocarcinoma of the rete testis include 1 ) tumor origin around the hilum , 2 ) no involvement of the tunica , 3 ) demonstration of transition from normal to tumor epithelium , and 4 ) no evidence of teratoma or any other primary tumor elsewhere in the body . our case fit 3 of these 4 diagnostic criteria : 1 ) , 2 ) , and 4 ) . a few cases have been examined immunohistochemically and are positive for cytokeratins and negative for beta - hcg , psa , and alpha - fetoprotein . positivity for cea may be seen , and it is helpful in excluding the diagnosis of mesothelioma . in our case , however , reliable markers that can define the origin of the adenocarcinoma as the rete testis have never been indicated . in advanced stages , adenocarcinoma of the rete testis is highly resistant to adjuvant radiotherapy and any known chemotherapy . the natural history of this tumor appears to be highly malignant , with 3- and 5-year disease - free survival rates of 49% and 13% , respectively .