| Abstract|| |
Adenocarcinoma of the rete testis is rare, and its etiology is unknown. The definite diagnosis merely depends on the exclusion of other tumors and histological features. We first describe a 38-year-old man with a carcinoma arising in the rete testis. The tumor was characterized by clear neoplastic cells and branching papillary growth. Focal stromal invasion and transition of normal rete epithelium to neoplastic cells were seen. The neoplastic cells were positive for epithelial membrane antigen, Ber-Ep4, vimentin, renal cell carcinoma marker, and CD10, while negative for Wilms' tumor 1, thyroid transcription factor-1, estrogen receptor, prostate specific antigen, placental alkaline phosphate, CD117, and alpha-1-fetoprotein. According to the above features, we diagnosed this tumor as adenocarcinoma of the rete testis. To our best knowledge, this is the first reported case of adenocarcinoma of the rete testis with prominently papillary structure and clear neoplastic cells. The rarity of adenocarcinoma of the rete testis and the unique features in our case cause diagnostic pitfalls. A complete clinicopathological study and thorough differential diagnosis are crucial for the correct result.
Keywords: Adenocarcinoma of the rete testis, clear cells, papillary
|How to cite this article:|
Huang PW, Chang KM. Adenocarcinoma of the rete testis with prominent papillary structure and clear neoplastic cells: Morphologic and immunohistochemical findings and differential diagnosis. Indian J Pathol Microbiol 2015;58:232-4
|How to cite this URL:|
Huang PW, Chang KM. Adenocarcinoma of the rete testis with prominent papillary structure and clear neoplastic cells: Morphologic and immunohistochemical findings and differential diagnosis. Indian J Pathol Microbiol [serial online] 2015 [cited 2020 Oct 29];58:232-4. Available from: https://www.ijpmonline.org/text.asp?2015/58/2/232/155328
| Introduction|| |
Adenocarcinoma of the rete testis is rare, and its etiology is unknown. The diagnosis is confirmed by morphology and exclusion of other tumors. Although recommended criteria and histological features for diagnosis are provided, the diagnostic dilemma still exists in clinical practice. We here propose a case of adenocarcinoma arising in the rete testis with unusual histological features. Literature is reviewed to exclude other morphologically similar tumors.
| Clinical Summary|| |
A 38-year-old man had found the left scrotum enlarged for a long period, worsening in recent 1-year. Physical examination revealed a painless and swollen left testis. The scrotal echogram showed the low pole of left testis destroyed by a cystic tumor. The computed tomography of whole abdomen revealed a hypodense mass, sized 2.5 cm 3 cm 5 cm, with calcified spots in the left lower testis. Laboratory investigations including serum β-human chorionic gonadotropin and alpha-fetoprotein (AFP) were within normal limit. A left radical orchiectomy was thus performed as diagnosis and treatment.
| Pathological Findings|| |
The specimen consisted of a testis with intact parietal tunica vaginalis, measuring 5 cm 3.5 cm 1.5 cm in size. There was a 3.5-cm, irregular-bordered tumor in the hilar region extending into the testicular parenchyma. The cutting surface of the tumor was tan white and spongy to firm in consistency [Figure 1]. Microscopically, the nonencapsulated tumor mostly restricted to the testicular hilum with intact visceral tunica vaginalis. The tumor invaded the seminiferous tubules and ductuli efferentes, which caused cystic dilation of ductuli efferentes and the caput portion of the epididymis. The other portions of the epididymis were unremarkable [Figure 2]. The tumor showed mainly branching papillary growth and occasionally tubulocystic pattern. Calcification or psammoma bodies were disclosed [Figure 3]. Focal stromal invasion was found as well [Figure 4]. The tumor cells were cuboidal to short columnar and had eosinophilic or clear cytoplasm, enlarged pleomorphic nuclei and nucleoli. The transition of normal rete epithelium to neoplastic cells was present [Figure 5]. Lymphovascular invasion was not identified. The immunohistochemical staining showed positive for epithelial membrane antigen (EMA), Ber-Ep4, vimentin, renal cell carcinoma marker (RCC), and CD10, while negative for Wilms' tumor-1 (WT-1), thyroid transcription factor-1, estrogen receptor (ER), prostate-specific antigen (PSA), placental alkaline phosphate (PLAP), CD117 and AFP [Figure 6]. Based on the above features, the diagnosis of adenocarcinoma of the rete testis was confirmed.
|Figure 1: (a) The testis has intact parietal tunica vaginalis. (b) An irregular-bordered tumor is in the hilar region and extends into the testicular parenchyma|
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|Figure 2: A nonencapsulated tumor is mainly in the testicular hilum and has intact visceral tunica vaginalis. The caput portion of the epididymis shows cystic dilation and is filled with colloid material. The other portions of the epididymis are unremarkable|
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|Figure 3: The tumor shows mainly branching papillary growth and occasionally tubulocystic pattern. Calcification or psammoma bodies are seen|
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|Figure 5: The tumor cells are cuboidal to short columnar and have eosinophilic or clear cytoplasm, enlarged pleomorphic nuclei and nucleoli. The transition of normal rete epithelium to neoplastic cells is present (right upper corner of a and b)|
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|Figure 6: The tumor cells are positive for (a) epithelial membrane antigen, and (b) renal cell carcinoma marker, while are negative for (c) Wilms' tumor 1, (d) prostate specific antigen, (e) placental alkaline phosphate ,and (f) alpha-1-fetoprotein|
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| Discussion|| |
Adenocarcinoma of the rete testis is a rare malignant tumor. There were approximately 30-70 reported cases. , The diagnosis depends on histological features and exclusion of other similar tumors. The most commonly recommended criteria were proposed by the Nochomovitz and Orenstein, including:
- No histologically similar extra-scrotal primary tumor,
- Intact parietal tunica vaginalis,
- Tumor centered on the testicular hilum,
- No evidence of any other primary testicular or paratesticular tumor, and
- Histological transition from normal to neoplastic rete epithelium. 
The immunohistochemical stains are useful to exclude metastatic tumors, other primary testicular and paratesticular tumors. In our case, the tumor was positive for EMA and negative for PLAP, CD117, AFP, and PSA, which excluded primary testicular germ cell tumors and metastatic prostatic carcinoma. , The morphology of this tumor and immunoreactivity with EMA, CD10, and RCC led a suspicion of metastatic papillary RCC. However, the RCC marker and CD10 are not absolutely specific for renal cell carcinoma. Many germ cell tumors and other neoplasm are positive for CD10. Some nonrenal tumors, such as breast carcinomas, parathyroid adenomas, and embryonal carcinomas, also show positivity for RCC.  However, there is no report about the immunoreactivity of RCC in the rete testis. Moreover, metastatic tumors in testis commonly show bilateral and/or multifocal involvement, conspicuous lymphovascular invasion or prominent interstitial pattern of growth. , In this case, these features were absent. The preoperation and postoperation computed tomography scan revealed no evidence of renal tumor or other metastatic sign.
The usual adenocarcinoma of the rete testis is composed of tumor nodules with permeating slit-like or bud-like papillary architecture. Our case showed prominently papillary growth pattern and clear neoplastic cells. Papillary cystadenoma of the epididymis, mesothelioma, papillary serous carcinoma, and clear cell carcinoma should be ruled out. The epididymis in this case only revealed cystic dilation of caput portion and no tumor growth. Malignant mesothelioma arises in the tunica vaginalis or tunica albuginea and forms multiple nodules coating or involving the thickened tunica vaginalis. The present tumor was solitary and confined in testis, and the tunica vaginalis was intact without tumor involvement. The immunohistochemical results also ruled out the diagnosis of malignant mesothelioma. The morphology of this tumor was similar to that of müllerian-type tumors such as papillary serous carcinoma and clear cell carcinoma. The müllerian-type tumors rarely occur in male patients. Less than 40 cases of serous tumor and two cases of clear cell carcinoma were reported. ,,, The histogeneses of müllerian-type tumors in testis and paratestis are not clear. Some hypotheses suggested müllerian-type tumors arising from epithelial cells of müllerian duct remnants, ,, and some authors speculated the tumors originating from müllerian metaplasia of the mesodermal epithelium. , In this case, there were no testiculoepididymal groove involvement and müllerian duct remnant. The neoplastic cells were negative for WT-1 and ER that were markers of müllerian epithelial neoplasm especially the serous carcinoma.  The transition of normal rete epithelium to neoplastic cells is supposed to be a distinguishing characteristic for primary adenocarcinoma of the rete testis. It was present in this case and confirmed the diagnosis.
The rarity of the primary malignancy in the rete testis limits the understanding of tumor variant and immunohistochemical profile, and causes the difficulty in diagnosis. However, the clinicopathological correlation and histological features are still the bases of diagnosis. Some series researches or molecular studies are needed to find out more reliable markers and features for differential diagnosis, and identify the etiology of adenocarcinoma of the rete testis.
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Dr. Kuo-Ming Chang
Department of Pathology, Mackay Memorial Hospital, No. 690, Sec. 2, Guangfu Rd, East Dist, Hsinchu City 30071, Taiwan
Republic of China
Source of Support: None, Conflict of Interest: None
[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6]