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Adenocarcinoma of the rete testis is rare and its etiological and pathologic characteristics are not well studied. We therefore investigated the clinical, morphologic, and immunohistochemical features of 6 cases diagnosed at our institution and conducted a detailed review of the literature. The mean age was 64 years. All patients presented with testicular masses; 4 were right-sided. On gross examination, all tumors were centered in the hilum and had solid and cystic cut surfaces. Microscopically, all had intrarete and invasive growth and showed multiple patterns, with a variable proportion of papillary, solid and glandular morphology, the latter varying from slit-like lumens to well-formed glands and tubules. Less common patterns included corded/trabecular (n=3), cribriform (n=3), glomeruloid (n=3), nested (n=2), and micropapillary (n=2). Discrete nests of eosinophilic and clear cells were a distinctive feature in 3 cases. Geographic necrosis occurred in 3 cases. All showed at least moderate nuclear pleomorphism with ovoid nuclei. Transition from benign to malignant rete epithelium was seen in all cases. The stroma was hyalinized to partially fibrotic. On immunohistochemical study, the tumor cells were positive for CK7 (5/5), AE1/AE3 cytokeratin (5/5), EMA (5/5), vimentin (5/5), EpCAM (detected by BerEP4 anitbody) (4/5), CK5/6 (4/5), nuclear Wilms Tumor-1 (4/5), epithelial specific antigen (detected by MOC31 antibody) (3/4), PAX8 (3/5), and calretinin (2/5). OCT3/4, SALL4, CD30, NKX3.1, PSA, α-inhibin, CK20, and S100 protein were negative. Ki-67 proliferative index ranged from 5% to 60% (mean: 40, median: 43). At presentation, 5 patients had retroperitoneal lymph node metastasis and one of these also had pulmonary metastases. The sixth patient developed pulmonary metastasis within 15 months of diagnosis. Three died within 4 years of diagnosis. In summary, adenocarcinoma of the rete testis is a rare malignant tumor with poor survival and a high propensity for retroperitoneal lymph node metastasis that must be distinguished from other testicular neoplasms and metastasis to the testis. Hilar localization, transition from benign to malignant rete epithelium, and supportive immunostains aid its accurate diagnosis.

Sertoliform cystadenoma of the rete testis (SCRT) is rare with only 9 cases reported to date in the literature, none with follow-up. Four large genitourinary pathology consult services were searched. We identified 15 cases of SCRT. Men were 21 to 84 years old (mean, 46 y) and had testicular discomfort or mass. Other findings were seminoma (n=1), spermatocele (n=2), hydrocele (n=1), varicocele (n=1), and scrotal hematoma (n=1). Eight had preoperative serum tumor markers, which were normal. Tumors ranged from 0.3 to 4 cm (mean, 1.5 cm). All of them were well circumscribed with solid and cystic features and occupied on average, 73% of the rete (20% to 100%). The tumors were mostly confined within dilated channels of the rete testis and showed classic features consisting of: (1) tubules with well-formed lumina in 87% of cases; (2) well-formed tubules with no lumina in 87% of cases; and (3) cords/nests in hyalinized or myxoid stroma in 73% of cases. Other patterns included: (1) solid/sheet growth in 26% of cases; (2) individual cells in 13% of cases; (3) festoons in 13% of cases; (4) branching tubules in 7% of cases; and (5) papillary in 7% of cases. Cells were cuboidal with round to oval nuclei with small nucleoli, except at the periphery where projections into rete tubules had a more columnar appearance. In the festooning pattern, nuclei were pseudostratified and columnar with prominent nucleoli and nuclear grooves. In 4 cases, tumor extended into adjacent seminiferous tubules surrounded by dense peritubular fibrosis, with in some cases small cysts lined by flattened epithelium containing pale lightly granular material. All cases lacked necrosis and significant atypia. Mitoses ranged from 0 to 2 per 10 high-power field. Follow-up ranged from 4 to 170 months with mean of 97 months. For the 13 cases with information, all patients were alive, except for 3 who died of either unrelated causes (9.2 and 10 y) or of unknown cause (4.8 y at age 89 y). We performed immunohistochemistry for steroidogenic factor 1 and inhibin in 4 of our cases, where 3 (75%) were positive for both markers. We also describe 2 additional cases which morphologically resembled SCRT but had more atypical features. This study highlights that SCRT has variable morphology. We also verify the benign nature of the lesion and its lack of association with any syndromes.

The present study aims to establish the nature and frequency of testicular lesions in the parenchyma adjacent to testicular germ cell tumors (TGCT) to improve understanding of the factors involved in the development of testicular cancer. Fifty-three cases of TGCT that were fixed in both neutral-buffered formalin and Bouin solution, allowing for the nuclear characterization of Sertoli cells (SCs), were included in this study. In each case, at least 3 sections of different areas of preserved parenchyma surrounding the TGCT were studied. We found Leydig cell hyperplasia, microlithiasis, angiopathy, adenomatous hyperplasia of the rete testis, SC nodules, SC dysgenesis and involution, SC-only tubules, tubular atrophy, adluminal compartment lesions, hypospermatogenesis associated with spermatocyte sloughing, spermatogonial maturation arrest, and hypertrophic and multinucleated spermatogonia. These lesions were found in regions both adjacent and far away from the tumoral mass, and abnormal seminiferous tubules were found intermingled with those showing complete spermatogenesis, suggesting that these lesions are primary and existed before the development of the tumor. Our study suggests that SCs might play a more important role in the development of testicular tumors than previously thought. Our data supports the hypothesis that there is an abnormal differentiation of SCs, caused either by genetic anomalies or by environmental agents during fetal life. This abnormal SC differentiation may cause not only primary spermatogenesis failure and spermatogenesis arrest at different levels, but may also contribute to the poor differentiation of gonocytes into spermatogonia. The abnormal gonocyte differentiation might favor the development of dysplastic germ cells that may later transform into intratubular germ cell neoplasia, unclassified type.