Review updates clinical management of testicular tumors in dogs

Version 2

A newly published review in Animals is sharpening the clinical playbook for canine testicular tumors, a common diagnosis in intact older male dogs. The review, led by researchers at the University of Padova and collaborating institutions, concludes that most cases are managed successfully with orchiectomy, but stresses that the real clinical stakes often center on endocrine effects, not metastatic behavior. In particular, the authors highlight the need to actively look for estrogen-secreting tumors that can trigger feminization syndrome and, in some dogs, life-threatening bone marrow suppression. (mdpi.com)

That framing matters because canine testicular tumors are common, but not uniform. The review notes that seminomas, interstitial Leydig cell tumors, and Sertoli cell tumors account for more than 95% of cases, typically in middle-aged to geriatric dogs. Prior work cited in the literature has also shown that risk rises with age and is higher in dogs with cryptorchidism, a long-recognized predisposing factor. Separate recent molecular work has underscored how much remains to be learned about tumor biology, including mitochondrial alterations across benign and malignant testicular tumors. (mdpi.com)

The review’s practical contribution is its stepwise approach to diagnosis and follow-up. It recommends physical examination and ultrasonography alongside endocrine assessment, including testosterone, estradiol, and the testosterone-to-estradiol ratio, plus preputial cytology as a tissue-level marker of estrogen effect. In the largest dataset referenced by the paper, dogs with Sertoli cell tumors had significantly higher estradiol concentrations and reduced testosterone-to-estradiol ratios compared with healthy controls. The authors also advise palpation of inguinal lymph nodes and ultrasound evaluation of medial iliac lymph nodes to assess for regional spread. (mdpi.com)

On treatment, the message is familiar but more nuanced than “remove both testicles.” Orchiectomy remains the standard of care for most canine testicular cancers, and the American College of Veterinary Surgeons separately lists testicular neoplasia and cryptorchidism among accepted indications for castration. But the review says unilateral orchiectomy can be considered in selected dogs when the opposite testis appears normal and preserving reproductive capacity or working ability still matters. That said, the tradeoff is more intensive surveillance: the authors recommend reassessing preputial cytology and hormone ratios about every four weeks after unilateral surgery, with ultrasound follow-up of the remaining testis and regional lymph nodes at three, six, and 12 months, then annually for at least two years. (mdpi.com)

The paper also gives clinicians a reminder about the small subset of dogs that become medically fragile before or after surgery. In dogs with estrogen-induced cytopenias, supportive care may include transfusions, antimicrobial therapy for neutropenic patients, fluid therapy, and close nursing support. The review notes that evidence for pharmacologic stimulation of hematopoiesis remains limited and inconsistent, with some dogs recovering after tumor removal alone. Prognosis is generally excellent when tumors are detected early and completely excised, but the authors stress that reversibility of estrogen-induced marrow injury is often the key determinant in more severe Sertoli cell tumor cases. (mdpi.com)

There doesn’t appear to be much formal outside commentary yet tied specifically to this review, but the broader literature supports its emphasis on individualized assessment rather than assuming every testicular mass behaves the same way. A 2024 molecular study described substantial heterogeneity in malignant canine testicular tumors, while a separate transcriptomic analysis of canine Leydig cell tumors found roughly 1,500 differentially expressed transcripts, including upregulation of steroidogenesis genes such as CYP11A1, STAR, and HSD3B1, as well as angiogenesis, extracellular matrix remodeling, cholesterol metabolism, and PI3K-Akt pathway signals. That study also pointed to potentially distinctive estrogen and relaxin signaling changes in Leydig cell tumors and suggested the possibility of future biomarkers or targeted therapies, reinforcing the idea that tumor typing and biologic behavior may become more clinically actionable as the evidence base grows. A recent histologic analysis likewise found mixed and multiple unilateral tumors are not unusual, reinforcing the value of careful pathology and follow-up planning. (mdpi.com, mdpi.com)

Why it matters: For general practitioners, surgeons, and oncology teams, this review is useful because it translates a familiar condition into a more structured management pathway. The biggest takeaway is that endocrine activity, especially hyperestrogenism, should drive urgency, perioperative planning, and post-op monitoring. For practices seeing intact senior males or cryptorchid dogs, the paper also reinforces the value of earlier detection through exam and imaging before complications such as feminization, marrow suppression, or contralateral disease emerge. The newer molecular data add a second message: even tumors that are often handled surgically may carry biologic differences that eventually improve classification, prognostication, and counseling. (mdpi.com)

What to watch: The next phase of research will likely focus less on whether to operate and more on which tumors carry endocrine risk, recurrence risk, or biologic differences that could change surveillance and counseling, especially as transcriptomic and mitochondrial profiling studies expand. In Leydig cell tumors specifically, pathways tied to steroid production, angiogenesis, extracellular matrix interactions, and PI3K-Akt signaling are now emerging as candidate areas for biomarker development and, potentially, future targeted approaches. (mdpi.com, mdpi.com)