Vas deferens to rete testis anastomosis for obstructive azoospermia.

PURPOSE: This video aims to present an in-depth, step-by-step tutorial on microsurgical reconstruction for obstructive azoospermia, featuring a distinctive case involving anastomosis from vas deferens to rete testis. The primary aim of this endeavor is to offer thorough and practical insights for healthcare professionals and researchers within the realm of reproductive medicine. The video endeavors to disseminate expertise, methodologies, and perspectives that can be advantageous to individuals grappling with obstructive azoospermia, providing a significant contribution to the progress of reproductive medicine and the augmentation of existing treatment alternatives. MATERIALS AND METHODS: Surgical footage was recorded using the ORBEYE 4K 3D Orbital Camera System by Olympus America, with patient consent acquired for research purposes. Additionally, a retrospective examination of patient records was undertaken to compile relevant medical histories. RESULTS: This video furnishes an exhaustive guide to microsurgical reconstruction for obstructive azoospermia, encompassing a distinctive instance of anastomosis from vas deferens to rete testis. State-of-the-art technology, such as the ORBEYE 4K 3D Orbital Camera, heightens procedural transparency, accentuating the significance of advanced instrumentation. The ethical underpinning is emphasized by obtaining patient consent for footage utilization, and a retrospective chart review augments the repository of valuable patient data. This comprehensive approach serves as an invaluable reservoir of knowledge for medical professionals and underscores excellence in clinical and ethical healthcare research. CONCLUSIONS: Anastomosis from vas deferens to rete testis emerges as a viable surgical reconstruction alternative for obstructive azoospermia, particularly when confronted with non-dilated tubules within the epididymis.

Three-dimensional analysis of junctions between efferent and epididymal ducts in the human caput epididymis.

BACKGROUND: Due to the scarcity of studies using human tissues, the limited information is currently available on the gross structure of the caput epididymis in humans, at which efferent ducts connect to the epididymal duct. OBJECTIVE: The present study investigated the three-dimensional structures of efferent and caput epididymal ducts in humans, with a focus on junctions between the former and the latter. MATERIALS AND METHODS: We examined three sets of human efferent and caput epididymal ducts in specimens obtained from prostatic carcinoma patients. They were reconstructed from serial paraffin sections using a segmentation model created by a deep learning protocol and high-performance three-dimensional reconstruction software. RESULTS: Serial sections and three-dimensional images of human efferent and caput epididymal ducts were combined to obtain the detailed anatomical information. When a single efferent duct was defined as a duct connecting to both the extra-testicular rete testis and epididymal duct, there were 14.7 efferent ducts with a total length of 3.0 m per specimen on average. The cranial portion of the efferent ducts joined to a single duct and terminated at the end of the epididymal duct, whereas other efferent ducts terminated independently on the side of the epididymal duct. These two types of junctions between the efferent and epididymal ducts differed in the patterns of the epithelial-type switch. The epididymal duct consisted of multiple segments, which were separated by a minimal amount of connective tissue septa or even without them. Efferent ducts occupied most of the volume of the caput epididymis. DISCUSSION AND CONCLUSIONS: By utilizing deep learning, we reconstructed human efferent and caput epididymal ducts and revealed their precise three-dimensional structures, which differed from those of rodents in several aspects. The present results may be useful for analyzing anatomical abnormalities related to some types of male infertility.

A comparative analysis of genes differentially expressed between rete testis cells and Sertoli cells of the mouse testis.

The rete testis (RT) is a region of the mammalian testis that plays an important role in testicular physiology. The RT epithelium consists of cells sharing some well-known gene markers with supporting Sertoli cells (SCs). However, little is known about the differences in gene expression between these two cell populations. Here, we used fluorescence-activated cell sorting (FACS) to obtain pure cultures of neonatal RT cells and SCs and identified differentially expressed genes (DEGs) between these cell types using RNA sequencing (RNA-seq). We then compared our data with the RNA-seq data of other studies that examined RT cells and SCs of mice of different ages and generated a list of DEGs permanently upregulated in RT cells throughout testis development and in culture, which included 86 genes, and a list of 79 DEGs permanently upregulated in SCs. The analysis of studies on DMRT1 function revealed that nearly half of the permanent DEGs could be regulated by this SC upregulated transcription factor. We suggest that useful cell lineage markers and candidate genes for the specification of both RT cells and SCs may be present among these permanent DEGs.

Rhox8 homeobox gene ablation leads to rete testis abnormality and male subfertility in mice†.

The reproductive homeobox X-linked (Rhox) genes encode transcription factors that are expressed selectively in reproductive tissues including the testis, epididymis, ovary, and placenta. While many Rhox genes are expressed in germ cells in the mouse testis, only Rhox8 is expressed exclusively in the Sertoli cells during embryonic and postnatal development, suggesting a possible role of Rhox8 in embryonic gonad development. Previously, Sertoli cell-specific knockdown of RHOX8 resulted in male subfertility due to germ cell defects. However, this knockdown model was limited in examining the functions of Rhox8 as RHOX8 knockdown occurred only postnatally, and there was still residual RHOX8 in the testis. In this study, we generated new Rhox8 knockout (KO) mice using the CRISPR/Cas9 system. Sex determination and fetal testis development were apparently normal in mutant mice. Fertility analysis showed a low fecundity in Rhox8 KO adult males, with disrupted spermatogenic cycles, increased germ cell apoptosis, and reduced sperm count and motility. Interestingly, Rhox8 KO testes showed an increase in testis size with dilated seminiferous tubules and rete testis, which might be affected by efferent duct (ED) Rhox8 ablation dysregulating the expression of metabolism and transport genes in the EDs. Taken together, the data presented in this study suggest that Rhox8 in the Sertoli cells is not essential for sex determination and embryonic testis differentiation but has an important role in complete spermatogenesis and optimal male fertility.

Exploring the anatomical factors influencing testes elasticity via ultrasound shear wave elastography: Preliminary results.

PURPOSE: The aim of this study is to evaluate the anatomical factors influencing elasticity values of normal testicular parenchyma using shear wave elastography (SWE). METHODS: This study examined 68 healthy male volunteers (117 testes in which standard transverse axis ultrasonography views could be obtained) via conventional scrotal ultrasonography and SWE. Both the mean (EMean) and standard deviation (ESD) elasticity values were acquired. RESULTS: In the standard transverse axis view of the rete testis at the mid-lateral edge of the testes, the EMean values in 2mm the testicular parenchyma from the rete testis and the testicular capsule at the same level as the rete testis were all significantly larger than in the central zone (P<0.001, P<0.001, respectively). The EMean value in the testicular parenchyma 2mm from the testicular capsule on the line formed approximately 45° below the horizontal line of the rete testis was significantly larger than in the rete testis approximately 45° above the horizontal line (P<0.001). In two standard transverse axis views, the ESD values in other regions were significantly larger than those in the central zones (all P<0.001). Also, the EMean values in the transmediastinal arteries were larger than those of the surrounding normal testicular parenchyma (P<0.001). CONCLUSION: Based on SWE, factors including the testicular capsule, the density of testicular fibrous septa, the depth of the Q-Box™, and the transmediastinal artery may influence the testes elasticity measurement.

Cystic dysplasia of the rete testis accompanying ipsilateral renal agenesis in a young adult: a case report.

A 31-year-old man with left-sided testicular pain lasting a couple of months was referred to our urology department due to a suspected testicular tumor. Physical examination showed a hard, thickened, and small left testis on palpation with a diffuse, inhomogeneous ultrasonographic appearance. After a urologic examination, a left-sided inguinal orchiectomy was performed. The testis, epididymis, and spermatic cord were sent to pathology. Gross examination revealed a cystic cavity filled with brown fluid and the surrounding brownish parenchyma measuring up to 3.5 cm in diameter. Histologic examination showed a cystically dilated rete testis lined with cuboidal epithelium and a positive immunohistochemical reaction to cytokeratins. Microscopically, the cystic cavity was a pseudocyst filled with extravasated erythrocytes and abundant clusters of siderophages. The siderophages extended into the testicular parenchyma, surrounding the seminiferous tubules and spreading out around the ducts of the epididymis, which were also cystically dilated with siderophages inside their lumina. On the basis of clinical data, histological, and immunohistochemical analysis, the patient was diagnosed with cystic dysplasia of the rete testis. The literature shows an association between cystic dysplasia of the rete testis and ipsilateral genitourinary anomalies. Therefore, our patient underwent a multi-slice computed tomography scan, which revealed ipsilateral renal agenesis, a right seminal vesicle cyst reaching up to the iliac arteries, and a multicystic formation cranial to the prostate.

Evaluation of tumour size and rete testis invasion in progression free survival of our patients with stage i testicular seminoma. A retrospective observational study of a reference hospital center and literature review.

INTRODUCTION: The aim of this study was to evaluate the impact of tumour size and rete testis invasion in progression free survival of our patients with stage I testicular seminoma. A literature review is also made. MATERIAL AND METHODS: A retrospective observational study was performed. We included patients with stage I seminoma between January 2010 and July 2022. Patients without factors of poor prognostic -Group A- were compared with patients with factors of poor prognostic -Group B-. Kaplan-Meier curves and log-rank testing were used to compare progression free survival (PFS) between these groups. Statistical significance was considered at P≤.05. RESULTS: 55 patients were included in this study. 20 patients (36.4%) were of good prognostic -Group A- and 35 (63.6%) had factors of poor prognostic -Group B-. The mean age was similar in both groups (mean±standard deviation), 38.62±9.04 years. The mean follow-up time was 63.5±33.6 months. All the patients in group A and 25.7% of the patients in group B underwent active surveillance (AS). 26 patients (74.3%) of the patients in Group B were treated with one cycle of adyuvant carboplatin. Three patients suffered a relapse with retroperitoneal lymph nodes (10.3%), all of them were treated with three cycles of BEP, with a complete response of the disease. No statistical significant differences were found in PFS between Group A and B (log Rank P=.317). CONCLUSION: Individualization of adjuvant treatment in stage I seminoma is important, avoiding the adverse effects derived from them.

Ultrasonographic evaluation of the rete testis thickness: a promising approach to differentiate obstructive from nonobstructive azoospermia.

This study aimed to evaluate the ability of rete testis thickness (RTT) and testicular shear wave elastography (SWE) to differentiate obstructive azoospermia (OA) from nonobstructive azoospermia (NOA). We assessed 290 testes of 145 infertile males with azoospermia and 94 testes of 47 healthy volunteers at Shanghai General Hospital (Shanghai, China) between August 2019 and October 2021. The testicular volume (TV), SWE, and RTT were compared among patients with OA and NOA and healthy controls. The diagnostic performances of the three variables were evaluated using the receiver operating characteristic curve. The TV, SWE, and RTT in OA differed significantly from those in NOA (all P ≤ 0.001) but were similar to those in healthy controls. Males with OA and NOA were similar at TVs of 9-11 cm 3 ( P = 0.838), with sensitivity, specificity, Youden index, and area under the curve of 50.0%, 84.2%, 0.34, and 0.662 (95% confidence interval [CI]: 0.502-0.799), respectively, for SWE cut-off of 3.1 kPa; and 94.1%, 79.2%, 0.74, and 0.904 (95% CI: 0.811-0.996), respectively, for RTT cut-off of 1.6 mm. The results showed that RTT performed significantly better than SWE in differentiating OA from NOA in the TV overlap range. In conclusion, ultrasonographic RTT evaluation proved a promising diagnostic approach to differentiate OA from NOA, particularly in the TV overlap range.

The abundance and localization of claudin-1 and -5 in the adult tomcats (Felis catus) testis, tubules rectus, rete testis, efferent ductules, and epididymis.

Tight junctions (TJ) are the anatomical component of blood-testis (BTB) and blood-epididymis (BEB) barriers and contain many proteins, including claudins. The presence of claudins in domestic cat testis and epididymis has not been previously described. This study aimed to determine whether claudin-1 and claudin-5 participate in the structure of BTB and BEB and whether their amounts differ between the testis and epididymal segments of adult cats, using Western blotting (WB) and immunohistochemistry. WB results demonstrated that claudin-1 was significantly lower in the testis than in all epididymal segments and higher in the corpus epididymis than in the cauda, while claudin-5 in the testis was significantly lower than in the caput and corpus. Claudin-1 was absent at the Sertoli-Sertoli junctions, while claudin-5 was detected at the level of the BTB during stages I and VIII. Both claudins were observed in the pachytene spermatocytes and the developing acrosome of the round and elongating spermatids. Claudin-5 was also detected in the cytoplasm of some spermatogonia, Sertoli cells, and late spermatid acrosome. In the epididymal segments, both claudins were localized to the area of the tight junctions and along the entire length of the lateral plasma membranes of adjacent principal cells and between principal and basal cells. These results may indicate that in the domestic cat, claudin-1 and -5 participate as both tight junction proteins and adhesion molecules in the BEB's structure, claudin 5 is a component of the BTB, and both proteins may be involved in postmeiotic germ cell development, especially acrosome development.

SOX17-positive rete testis epithelium is required for Sertoli valve formation and normal spermiogenesis in the male mouse.

Seminiferous tubules (STs) in the mammalian testes are connected to the rete testis (RT) via a Sertoli valve (SV). Spermatozoa produced in the STs are released into the tubular luminal fluid and passively transported through the SV into the RT. However, the physiological functions of the RT and SV remain unclear. Here, we identified the expression of Sox17 in RT epithelia. The SV valve was disrupted before puberty in RT-specific Sox17 conditional knockout (Sox17-cKO) male mice. This induced a backflow of RT fluid into the STs, which caused aberrant detachment of immature spermatids. RT of Sox17-cKO mice had reduced expression levels of various growth factor genes, which presumably support SV formation. When transplanted next to the Sox17+ RT, Sertoli cells of Sox17-cKO mice reconstructed the SV and supported proper spermiogenesis in the STs. This study highlights the novel and unexpected modulatory roles of the RT in SV valve formation and spermatogenesis in mouse testes, as a downstream action of Sox17.

KMT2C mutation in a Chinese man with primary multidrug-resistant metastatic adenocarcinoma of rete testis: a case report.

BACKGROUND: Adenocarcinoma of the rete testis (AORT) is an extremely rare malignant tumor with poor prognosis and limited responsiveness to traditional chemotherapy. Few previous studies have focused on the molecular mechanisms underlying therapy resistance in AORT and further scrutiny is required to enable searches for targeted drugs to guide treatment selection. CASE PRESENTATION: The current case concerns a 55-year-old man with AORT who presented with isolated bone metastasis at initial diagnosis and experienced rapid disease progression after multi-line platinum-based combination chemotherapy. Next-generation sequencing revealed a novel somatic lysine methyltransferase 2C (KMT2C) c.5605 T > C mutation in exon 36 with an abundance of 49.27%. The patient received antiangiogenic drug treatment for 2 months but this was discontinued due to unacceptable anorexia and nausea. He survived for 12 months after diagnosis. CONCLUSION: A potential correlation between AORT primary multi-drug resistance and KMT2C mutations is implied. Further studies are needed to determine the efficacy of PARP1/2 inhibitors for tumors with KMT2C mutations.

Clinicopathologic features and proposed grossing protocol of orchiectomy specimens performed for gender affirmation surgery.

Gender affirmation surgery performed for gender dysphoria is increasing to instigate changes more closely approximating gender identity. We investigated the clinicopathologic features of gender-affirming orchiectomies performed at our institution and devised a grossing protocol for these increasingly encountered specimens. We obtained 45 orchiectomies from 23 patients and reviewed clinicopathologic features. The number of sections per case was noted and reviewed to devise an optimal grossing protocol to assess pathologic findings. Twenty-three patients had bilateral orchiectomy with 1 unilateral. The average patient age was 39.4 years (range, 21-71 years); all received hormones for a mean of 66.1 months (range, 12-348 months). The average number of slides per orchiectomy was 8 slides (range, 1-11). Aspermatogenesis occurred in 32 (71%), hypospermatogenesis in 8 (18%), and normal spermatogenesis in 5 (11%) testes. Twenty-five (56%) exhibited scattered cells with nuclear cytomegaly, concerning for germ cell neoplasia in situ (GCNIS), but OCT4 negative. Six (13%) had multinucleated stromal cells. Leydig cells were markedly reduced/absent in 38 testes (85%). Epithelial hyperplasia was identified in 15 rete testes (33%) and 24 epididymes (53%), while 18 (40%) showed periepididymal muscular hyperplasia. All findings were identified in the initial 2 slides including rete testis/epididymis, except for 3 cases, missing only focal tubular sclerosis. Despite all received treatment, only a subset showed changes of exogenous hormone therapy. The presence of nuclear cytomegaly can mimic GCNIS and may be a potential pitfall. Two sections to include rete testis/epididymis and a third of cord margin are sufficient to identify the relevant pathology and germ cell tumors overall are uncommon in orchiectomies performed for gender affirmation.

Three-dimensional analysis and in vivo imaging for sperm release and transport in the murine seminiferous tubule.

Spermatozoa released from Sertoli cells must be transported to the epididymis. However, the mechanism of the luminal flow in seminiferous tubules has remained unclear to date. Therefore, in this study, we investigated luminal flow and movements in the seminiferous tubules by three-dimensional analysis and in vivo imaging. Serial 5-µm-thick mouse testicular sections at 50-µm-intervals were prepared and stained by Periodic Acid-Schiff-hematoxylin. After three-dimensional reconstruction of the seminiferous tubules, the localization of the released spermatozoa and the stages observed in the sections were recorded in each reconstructed tubule. Luminal movements in the seminiferous tubules were observed by in vivo imaging using a fluorescent-reporter mouse and two-photon excitation microscopy system. Spermatozoa without contact to the seminiferous epithelium were not accumulated toward the rete testis. Additionally, such spermatozoa were found on their way not only to the most proximal rete testis but also a more distant rete testis from any stage VIII seminiferous epithelia. In vivo imaging demonstrated that the direction of the flagella of spermatozoa attached to the seminiferous epithelium was repeatedly reversed. The epithelium at the inner curve of the seminiferous tubule was shaken more actively and had fewer spermatozoa attached compared with the epithelium at the outer curve. Our results hence suggest that the luminal flow in the seminiferous tubules is repeatedly reversed and that this physical force helps spermatozoa to be released from Sertoli cells. In brief: Spermatozoa are released from Sertoli cells and flow in the seminiferous tubule to the rete testis. Our results suggest that the luminal flow in the tubules is repeatedly reversed and that this physical force helps spermatozoa release from the Sertoli cells.

Molecular analysis of adenocarcinomas of the rete testis demonstrates frequent alterations in genes involved in cell cycle regulation.

Adenocarcinomas of the rete testis (ACRT) are rare and aggressive testicular neoplasms that present predominantly in older men and have a tendency for early systemic spread. Their morphology spans a wide spectrum, including tumors with glandular, solid, papillary, micropapillary, glomeruloid, cribriform, and sarcomatoid growth patterns, or a combination thereof. The genomic alterations associated with these tumors have not been studied previously. We assessed eight ACRT published in prior clinicopathologic series using a solid tumor DNA sequencing panel. Pathogenic variants were identified in 6/8 cases. More specifically, four cases demonstrated inactivation of genes involved in cell cycle regulation, including CDKN2A, BAP1, TP53, and RB1. CDKN2A was the only recurrently affected gene, with pathogenic variants detected in 3/8 cases. One of these three cases had molecular evidence of concurrent homozygous (i.e. biallelic) NF2 inactivation by a frameshift variant and loss of the wildtype copy of the gene. One case had an internal tandem duplication in AKT, which has been previously described in juvenile granulosa cell tumor and sclerosing pneumocytoma and results in downstream activation of PI3K signaling. The remaining case with positive molecular findings harbored two concurrent truncating SETD2 variants. Multiple arm-level and chromosome-level copy number events were present in 3/8 cases, all of which harbored variants in genes involved in cell cycle regulation. In summary, ACRT are rare tumors with frequent inactivation of genes that play a major role cell cycle regulation, and a subset harbors variants that are potentially amenable to targeted therapy.

[ADENOCARCINOMA OF THE RETE TESTIS WITH METASTASIS OF THE PENILE AND LUNG: A CASE REPORT].

Adenocarcinoma of the rete testis is a rare malignant tumor with poor prognosis. We report a case of adenocarcinoma of the rete testis. A 55-year-old man became aware of discomfort in the right scrotum. Negative results were obtained for the serum markers AFP, ß-human chorionic gonadotropin (ß-HCG), and LDH. Computed tomography (CT) showed enhancement of the right testis. Radical orchiectomy was performed. Immunohistochemical examination of the resected specimen showed positive results for CEA, and adenocarcinoma of the rete testis was diagnosed. Serum CEA level was elevated. CT showed swelling of the para-aortic lymph nodes. Retroperitoneal lymph node dissection (RPLND) was performed, and serum CEA then normalized. The patient developed penile metastases 4 months after RPLND, and serum CEA level again increased. Total penile resection was performed. TIP (Paclitaxel, Ifosfamide, Cisplatin) therapy was started after lung metastasis and increased serum CEA were identified. CT after 2 cycles of TIP therapy revealed disappearance of lung metastasis and normalization of serum CEA. Five months later, CT showed recurrence of lung metastases.

Three-dimensional analysis of mesonephric tubules remodeling into efferent tubules in the male mouse embryo.

BACKGROUND: Spermatozoa are transported to the epididymal duct through efferent tubules. Although the origin of the efferent tubules is thought to be mesonephric tubules (MTs), their detailed developmental process, for example, where the rete testis and efferent tubules are connected, is unclear. We investigated the structural changes of the MTs in the male mouse embryo using a three-dimensional reconstruction method. RESULTS: Three to six MTs were connected to the Wolffian duct, and some of them branched, resulting in five to nine tips. Rete cells contacted the three to six tips. The MTs showed a folded shape when the gonadal fate was determined. After the testis development started, they became short and straight but emerged as long and twisting by birth. Before birth, the efferent duct was composed of MTs and a cranial portion of the folded Wolffian duct. CONCLUSIONS: The contact between the rete testis and efferent tubules is possibly established at the tip of each MT. The MTs regress after gonadal fate is determined but is remodeled to the twisting efferent tubules by birth. The efferent tubules are composed of the MTs but also a cranial portion of the folded Wolffian duct in the mouse.

A possible highway system for the rapid delivery of sperm from the testis to the penis in the naked mole-rat, Heterocephalus glaber.

Gametogenesis is suppressed in most members of the eusocial naked mole-rat (NMR) colony, while the queen selects mainly one breeding male during her life span. Recently, it was reported that the NMR testicular organization seems to produce spermatozoa on demand after suppression of spermatogenesis during most of gestation. A Sertoli cell "pump" is then used to flush the spermatozoa into short tubuli recti and simplified rete testis to reach the excurrent duct system. We hypothesize that the components of this duct system are adapted for rapid delivery of spermatozoa to the penis and for numerous copulations with the queen. Therefore, the aim was to study the ultrastructure of the male NMR reproductive duct system using light microscopy and transmission electron microscopy. The NMR rete testis gives rise to six to eight efferent tubules joining the caput epididymis. The caput epididymis resembles that of other rodents but with less distinction in terms of histological zoning. The remainder of the epididymis is considerably reduced in length compared to other rodents. In contrast, the vas deferens epithelium is highly specialized in that a vast range of vesicles, often closely associated with the spermatozoa, were visible. The large ampulla is a factory for merocrine and apocrine secretions, producing even more diverse vesicles. The transitional epithelial cells of the bladder appear to secrete abundant mucous and the penis as well as its baculum is relatively small. We speculate that these modifications strongly suggest that the excurrent duct system has been simplified and adjusted to compensate for the absence of long maturation and storage of spermatozoa. We propose that these adaptations to the NMR reproductive tract are associated with a state of degenerative orthogenesis that was selected for due to the absence of sperm competition and apparently rapid delivery of spermatozoa from the testis.

Tubular ectasia of the rete testis in an Angus bull.

An 18-month-old Angus bull presented to Auburn University College of Veterinary Medicine for a routine breeding soundness evaluation and lameness evaluation. He was classified as deferred potential breeder due to a lameness and was donated to the university. Following treatment, the bull's lameness resolved. He passed the breeding soundness examination in accordance with the Society for Theriogenology standards. However, avascular dilated areas at the level of the mediastinum testis of the right testicle were detected via Doppler ultrasonography. A high level of vascularity is routinely seen with neoplasia, such as teratomas. Due to the lack of vascularity, a presumptive diagnosis of tubular ectasia of the rete testis was made. The bull was castrated. The right testicle was submitted for histopathology revealing a definitive diagnosis of tubular ectasia of the rete testis.

Carcinoma of the rete testis: A rare testicular tumor.

Carcinoma of the rete testis is a rare malignant tumor which frequently occurs in middle-aged to older patients and has an aggressive biological behavior. We present the case of a 57-year-old man who presented with an ill-defined mass in the right testicle. The patient underwent a radical orchidectomy. Microscopic evaluation showed a neoplasm displaying a complex papillary-cystic architecture, infiltrating the testicular parenchyma. An in situ proliferation of neoplastic cells, with nuclear stratification and scanty cytoplasm was seen at the periphery, within the channels of the rete testis. The tumor infiltrated the tunica albuginea focally without disrupting it completely. Immunohistochemistry was positive for AE1/AE3, CK7, CK34ßE12, D2-40, and PAX8. Imaging studies presented no evidence of metastatic disease. These findings are those of a primary rete testis carcinoma. The transition between benign and neoplastic rete testis epithelium served as a helpful diagnostic clue. Metastatic carcinomas from other sites were considered in the differential diagnosis.