5th International Andrology Symposium
5th International Andrology Symposium
Darius Dasevičius
Institute for Pathology, National Centre of Pathology, Affiliate of Vilnius University Hospital Santariskiu Klinikos, 08406 Vilnius, Lithuania.
Correspondence: Dr med Darius Dasevicius Faculty of Medicine, Vilnius University, Vilnius, Lithuania
Cryptorchidism—testicular maldescent—affects 2–5% of newborn boys and ~1% at 12 months, and is linked to infertility and increased testicular germ cell tumor risk in adulthood. Histopathology provides the closest “ground truth” for prognosis, because tissue read-outs (germ cell number per tubule, presence of adult dark [Ad] spermatogonia, Sertoli-cell–only [SCO] patterns, interstitial changes) integrate upstream endocrine and paracrine events and the thermal microenvironment. This proceedings paper reviews the classical and modern histopathology of cryptorchid testes (as seen on light microscopy), highlights the methodological importance of optimized fixation and semithin resin sections for identifying Ad spermatogonia, synthesizes how biopsy metrics stratify fertility risk, and summarizes the pathology of germ cell neoplasia in situ (GCNIS) in this setting. We also integrate cohort data from Vilnius–Basel collaborations and others showing that unilateral cryptorchidism often behaves as a bilateral disease at the tissue level and that the presence or absence of Ad spermatogonia (and related indices) outperforms routine serum hormones for individual fertility prediction. Finally, we propose a practical reporting template for pediatric testicular biopsies taken at orchiopexy that preserves clinical decision-making value (fertility risk, need for endocrine induction of mini-puberty, timing of surveillance for malignancy) while respecting tissue limits and safety.
Key words Cryptorchidism histology ad spermatogonia mini puberty
La cryptorchidie—maldescente testiculaire—touche 2 à 5 % des nouveau-nés de sexe masculin et environ 1 % à 12 mois, et s’associe à une infertilité accrue et à un risque majoré de tumeur germinale testiculaire à l’âge adulte. L’histopathologie constitue l’indicateur pronostique le plus fiable, car les paramètres tissulaires (nombre de cellules germinales par tube, présence de spermatogonies adultes sombres [Ad], aspects de type Sertoli-cell-only [SCO], modifications interstitielles) reflètent l’ensemble des événements endocrines, paracrines et thermiques antérieurs.
Cet article de synthèse passe en revue l’histopathologie classique et contemporaine des testicules cryptorchides en microscopie optique, souligne l’importance d’une fixation optimisée et des coupes semi-fines en résine pour l’identification des spermatogonies Ad, et montre comment les indicateurs histologiques permettent de stratifier le risque de fertilité. La pathologie de la néoplasie germinale in situ (GCNIS) dans ce contexte est également résumée. Nous intégrons les données de cohortes, notamment des collaborations Vilnius–Bâle, indiquant que la cryptorchidie unilatérale présente fréquemment un phénotype bilatéral au niveau tissulaire et que la présence ou l’absence de spermatogonies Ad constitue un meilleur prédicteur individuel de fertilité que les hormones sériques usuelles. Enfin, nous proposons un modèle pratique de compte rendu anatomopathologique pour les biopsies testiculaires pédiatriques réalisées lors d’une orchidopexie, afin d’optimiser la valeur décisionnelle (risque de fertilité, indication d’induction endocrine de la mini-puberté, stratégies de surveillance oncologique) tout en respectant les contraintes tissulaires et la sécurité.
Mots-clés: Cryptorchidie, histologie, spermatogonies Ad, mini-puberté
Why scrutinize the histology of cryptorchid testes? First, because adult fertility correlates strongly with whether the infant testis establishes a pool of Ad spermatogonia during mini-puberty, a developmental window in which luteinizing hormone (LH) and testosterone peak and Sertoli cell function is calibrated. Failure of gonocyte→Ad transformation yields a depleted stem-cell reservoir and predicts poor semen parameters decades later—even if orchiopexy is anatomically successful. Histology captures this failure directly. Large clinicopathologic series confirm that quantifying germ cells per tubule and documenting Ad spermatogonia during childhood stratifies azoospermia risk and informs therapy. [1–4]
Second, histology remains the only practical way to diagnose GCNIS (the universally accepted precursor to most post-pubertal testicular germ cell tumors) in equivocal settings, and to document ancillary risk features (multinucleated spermatogonia, tubular atrophy/fibrosis). Consensus taxonomies and ISUP/WHO 2016 nomenclature standardize these entities and their reporting. [5–7]
Finally, histology is a bridge between basic and clinical science. It is where the “HPG-axis hypothesis” and the “primary testicular dysgenesis hypothesis” leave footprints (Leydig cell size/number, Sertoli cell maturation, tubular architecture, interstitium), and where the consequence of temperature and timing is recorded in resin and glass. [2,3,8]
Routine 10% neutral buffered formalin (NBF) paraffin processing, while ubiquitous, introduces shrinkage and sloughing artifacts that obscure germ cell cytology in infant testes; it often prevents reliable discrimination between Ad and Ap spermatogonia. [9] For fertility-oriented pediatric testis biopsies, semithin (0.5–1 μm) sections of epoxy-resin–embedded tissue stained with toluidine blue preserve subcellular detail and allow confident identification of spermatogonial subclasses. This technique, refined in andrology and NOA (non-obstructive azoospermia) practice, is considered the most suitable approach for evaluating spermatogenesis histologically. [10-13]
Key technical points:
Germ cells. The signature lesion is depletion of germ cells with failure of gonocyte→Ad transformation. Under light microscopy (semithin, toluidine blue), Ad spermatogonia are recognized by their dense, spherical nuclei with a characteristic perinuclear rarefaction halo and clumped chromatin—features that are difficult to appreciate in paraffin H&E but crisp in resin sections. Their absence defines a high infertility risk (HIR) phenotype; presence (≥1 Ad per ≥1 tubule) indicates low infertility risk (LIR)—a dichotomy repeatedly validated against semen outcomes. [2–4,10,15]
Sertoli cells. Cryptorchid testes often show developmental arrest of Sertoli cells: tall cells with immature cytoplasm, persistent fetal markers, and loss of proper polarity; SCO patterns may appear in the most severe cases. [1–3,5]
Leydig cells. Contrary to the lay expectation of Leydig hyperplasia, pediatric cryptorchid testes frequently exhibit Leydig cell atrophy and vacuolization on semithin sections—an anatomic correlate of impaired LH-Leydig signaling during mini-puberty in a subset of boys. [1–3,10,14]
Tubulointerstitium. Early peritubular fibrosis, basement membrane thickening, and reduced tubular diameter track with germ cell loss. Interstitial edema can be seen in acute torsion/iatrogenic injury but is not a hallmark of ordinary maldescent. [1–3,5]
Sertoli-cell–only (SCO) / extreme HIR: essentially no recognizable spermatogonia; severe tubular atrophy/fibrosis. [1–3,5]
Fig.A. Marked shrinkage artifacts are evident within the germinal epithelium. Proper identification of Ad spermatogonia is barely possible. Formalin fixed, Paraffin embedded tissue. H&E staining, 40x. Fig.B. Low Infertility Risk. All tubular cross-sections have spermatogonia, some – Ad spermatogonia (long arrow); broad interstitium with several atrophic Leydig cells (short arrows). Toluidine staining, 40x. Fig.C. High Infertility Risk. Diffuse decrease of tubular density. Severe germ cell depletion (arrows). No Ad spermatogonia. Mostof the tubules contain only Sertoli cells (5-star). Toluidine staining, 40x. Fig.D. High infertility risk. All tubules contain only Sertoli cells (5-stars), with no spermatogonia observed. Toluidine staining, 40x.
The contralateral “normal” testis in unilateral cryptorchidism frequently shows subclinical abnormalities (lower G/T, rare Ad, subtle SC dysmaturation) consistent with a bilateral disease model—one reason unilateral cases can still have reduced adult semen quality. [1,14]
Across classic and modern studies, Ad presence in infancy/early childhood is the strongest histologic predictor of adult sperm output. The Fertility Index (fraction of tubules containing any spermatogonia) complements G/T and AdS/T to capture both distribution and depth of the germ-cell deficit. A meta-analytic theme is consistent: Ad+ cryptorchid boys fare far better than Ad− peers, even when both receive early orchiopexy. [15–17]
These indices also serve as biomarkers of response to endocrine therapy. In randomized/controlled settings, GnRH agonist (LH-RHa) or gonadotropin regimens administered around mini-puberty increased G/T and converted some Ad− testes to Ad+, whereas surgery alone did not. [2,3,18,19]
Histology also speaks to mechanism. The HIR pattern (Ad−, Leydig atrophy, preserved FSH-Sertoli drives with failing LH–Leydig output) aligns with a mini-puberty insufficiency endotype. Tissue-level rescue after LH-RHa, including transcriptomic reprogramming of chromatin modifiers (e.g., PRDM family HMTs), has been documented in Vilnius–Basel cohorts, providing molecular plausibility for the histologic changes we see. [2,3]
A recent work further argues that temperature alone is insufficient to explain the failure of Ad formation: with LH-RHa, differentiation to Ad occurred despite cryptorchid position, indicating that endocrine milieu can override thermal disadvantage at this developmental stage. [3]
Formerly “CIS/IGCNU/TIN,” germ cell neoplasia in situ (GCNIS) is the WHO-endorsed precursor of most post-pubertal TGCTs. Histologically, large atypical germ cells with
abundant pale cytoplasm and prominent nucleoli line the basal compartment of seminiferous tubules; immunoprofiles include PLAP, OCT3/4, and c-KIT positivity. [5-7]
Prevalence in cryptorchid adult testes is variably reported from ~1.7% to 8%, with several biopsy series centering around ~3%, acknowledging selection and sampling biases. [20-23] Importantly, ~50% of men with biopsy-proven GCNIS will develop invasive cancer within ~5 years without treatment, which underpins surveillance and management recommendations. [20,21]
Does orchiopexy abolish cancer risk? No. Early orchiopexy appears to reduce relative risk compared with post-pubertal repair, but does not eliminate it; hence lifelong awareness and self-examination are recommended. [24–26]
Other malignancy-adjacent histologies
When a pediatric testicular biopsy is performed at orchiopexy (in experienced centers, with prior counseling), the pathology report should prioritize fertility risk and malignancy surveillance implications while documenting background features that hint at mechanism.
Suggested minimum dataset:
Surgery is necessary but not sufficient. Orchiopexy relocates the testis and eases surveillance but does not rebuild a missing Ad pool. Histology can show whether surgery is likely to “ride the wave” of intact biology (Ad+) or needs endocrine rescue (Ad−). [1–4,18–19]
When Ad is absent (HIR), evidence supports considering GnRH agonist (or gonadotropin) protocols to “induce mini-puberty,” with tissue-level and later semen benefits in selected cohorts. [2,3,18,19]
When GCNIS is found, urologic-oncologic algorithms apply (radiation in selected cases vs surveillance vs orchiectomy, depending on age, fertility plans, and contralateral status). [5–7,20–21,24–26]
Sampling bias (tiny biopsies in a mosaic organ), assay variability (non-standardized counts), and processing heterogeneity (paraffin vs resin) complicate cross-study comparisons. Prospective registries using harmonized semithin protocols, age-matched norms, and blinded central review are needed. On the translational side, single-cell/spatial transcriptomics pre-and post-endocrine rescue can connect histologic rescue (Ad appearance) to gene-program activation (e.g., chromatin remodelers such as PRDM HMTs). [2,3]
Pathology can deliver clinically decisive information if we give it the right tissue, processed the right way, and if we ask the right questions. In cryptorchidism, the question is not only “where is the testis?” but “what is inside it, now, at this age?”—and what that portends for this child’s future fertility and cancer risk. The semithin-resin approach makes Ad visible; the counts make risk quantifiable; and the vocabulary (GCNIS) makes risk shareable. That—together with multidisciplinary decision-making—is the core message from our Vilnius practice and the European collaborations we are grateful to contribute to. (Conference transcript)
The author thanks colleagues in Vilnius and Basel and the pediatric urology teams who collect biopsies with rigor and care. Professional training in histopathology included an internship at University Hospital Basel.
Lorem ipsum dolor sit amet consectetur. Id mollis nulla maecenas at vestibulum blandit consectetur. Vulputate libero turpis diam eu rhoncus arcu. Donec at imperdiet viverra ut eu sagittis nunc volutpat. Sem nisi turpis venenatis non sed adipiscing donec dignissim.