Ovarian Tumors

Ovarian tumors in mares represent abnormal growths arising from various cell types within the ovary, ranging from benign masses with minimal health impact to aggressive malignancies that threaten both fertility and life. The ovary contains multiple tissue types including germ cells, sex cord-stromal cells, and epithelial cells, each capable of giving rise to distinct tumor varieties with characteristic behaviors and clinical presentations. Understanding ovarian tumors is essential for mare owners, breeding managers, and equine veterinarians, as these conditions significantly impact reproductive function and may cause dramatic behavioral changes that affect mare usefulness and welfare.

Ovarian tumors occur across all horse breeds and ages, though certain tumor types show predilection for specific age ranges. Granulosa cell tumors, the most common ovarian tumor in horses comprising approximately eighty-five percent of cases, typically affect mares between five and nine years of age but can occur from young adulthood through old age. Teratomas tend to develop in younger mares, while other tumor types show variable age distributions. No definitive breed predisposition has been established for most ovarian tumors, though individual studies have suggested possible increased incidence in certain populations. Both reproductively active broodmares and maiden mares can develop ovarian tumors.

The impact of ovarian tumors on mare health and functionality varies dramatically based on tumor type and hormonal activity. Many ovarian tumors, particularly granulosa cell tumors, produce hormones that disrupt normal reproductive cycling and cause profound behavioral changes. Affected mares may display persistent estrus behavior, complete lack of cycling, or stallion-like aggression depending on the specific hormones produced. These behavioral changes often render mares unsuitable for their intended use, whether breeding or performance, independent of any direct health threats. Large tumors may cause abdominal discomfort, and malignant varieties can metastasize to other organs with serious systemic consequences.

Fortunately, most ovarian tumors in mares are treatable through surgical removal of the affected ovary, with excellent prognosis for return to normal function when the condition is recognized and addressed appropriately. Granulosa cell tumors, despite their size and dramatic hormonal effects, are almost universally benign and curable with ovariectomy. Early detection through regular reproductive examination allows intervention before tumors reach sizes that complicate surgical removal. Following successful surgery, the contralateral ovary typically resumes normal function within several months, restoring fertility in most cases. Even mares with less common malignant tumor types may benefit from surgical treatment combined with appropriate monitoring for recurrence or metastasis.

The primary causes of ovarian tumor development in mares involve complex cellular processes leading to uncontrolled growth of specific ovarian cell populations. Granulosa cell tumors arise from the granulosa cells that normally line ovarian follicles and produce estrogen, with unknown triggers initiating their transformation from normal functional cells to neoplastic growth. Teratomas develop from germ cells capable of differentiating into multiple tissue types, resulting in bizarre tumors containing hair, teeth, bone, and other tissues. Epithelial tumors originate from the surface cells covering the ovary, while other rare tumor types arise from their respective cell lineages. The specific molecular events initiating transformation remain poorly understood in equine ovarian tumors.

Genetic and breed predispositions for ovarian tumors have not been definitively established in horses, though some evidence suggests possible heritable factors. Individual mare variation in tumor susceptibility may have genetic components that remain uncharacterized. Certain family lines might demonstrate increased ovarian tumor incidence, though systematic studies are lacking. No genetic tests currently exist to identify mares at increased risk for ovarian tumor development. The sporadic nature of most cases suggests that if genetic factors contribute, they likely interact with environmental or random factors rather than following simple inheritance patterns.

Environmental and management factors potentially contributing to ovarian tumor development remain largely unidentified in equine medicine. Unlike some species where exogenous hormone exposure or environmental toxins have been linked to reproductive tumors, no such associations have been established in horses. Reproductive history including number of pregnancies, breeding age, and use of reproductive hormones has not been convincingly linked to ovarian tumor risk in mares. The relatively low incidence of ovarian tumors despite widespread use of reproductive technologies suggests that common management practices do not significantly increase risk. Research into potential environmental contributors continues but has not yielded actionable findings.

Risk factors for equine ovarian tumors are poorly defined due to the condition's relative rarity and sporadic occurrence. Age represents the most consistent factor, with granulosa cell tumors showing peak incidence in middle-aged mares. Previous ovarian abnormalities or hormonal disturbances have not been established as risk factors. Neither reproductive status (maiden versus broodmare) nor specific use (racing, showing, pleasure) shows clear association with tumor development. The unpredictable nature of ovarian tumor occurrence makes identification of at-risk populations difficult, reinforcing the importance of regular reproductive examination for all mares regardless of perceived risk level.

The pathophysiology of ovarian tumor development involves progressive accumulation of cellular abnormalities leading to uncontrolled proliferation. In granulosa cell tumors, affected cells escape normal regulatory mechanisms controlling growth and hormone production, resulting in tumor expansion and often excess steroid synthesis. These tumors typically suppress the contralateral ovary through hormone feedback mechanisms, causing it to become small and inactive. Teratoma development involves germ cells undergoing differentiation into multiple tissue types without appropriate spatial organization, creating chaotic masses of varied tissues. Malignant tumors additionally acquire capabilities for tissue invasion and metastatic spread, though such aggressive behavior is uncommon in equine ovarian tumors. Understanding these processes guides both diagnostic approaches and treatment planning.

Early warning signs of ovarian tumors in mares often involve subtle changes in reproductive behavior that precede obvious tumor detection. Initial indications may include mild irregularities in estrous cycling, with cycles becoming slightly longer or shorter than the mare's established pattern. Some mares show increased irritability or sensitivity to handling around the flank region before other signs develop. Changes in athletic performance may occur in competition mares, with affected individuals showing decreased willingness to work or unexplained performance decline. These early signs are easily attributed to other causes, making early ovarian tumor detection dependent on regular reproductive examination rather than symptom recognition.

Common symptoms of established ovarian tumors center on reproductive and behavioral abnormalities driven by hormonal dysfunction. Granulosa cell tumors typically produce either estrogen, testosterone, or inhibin (or combinations), leading to diverse presentations. Estrogen-producing tumors cause prolonged estrus behavior, with affected mares showing constant receptivity to stallions, frequent urination posturing, and vulvar winking lasting weeks or months. Testosterone-producing tumors cause stallion-like behavior including aggression, mounting other mares, dropped clitoral appearance, and even physical masculinization with neck crest development. Inhibin-producing tumors suppress reproductive cycling entirely, with mares showing no estrous behavior despite appropriate season and management.

Behavioral changes associated with ovarian tumors can dramatically impact mare usefulness and handling safety. Mares with estrogen-producing tumors may become difficult to handle during what would normally be diestrus periods, showing distraction and poor focus. Those with testosterone production often become dangerous, exhibiting unprovoked aggression toward handlers, other horses, and particularly toward mares in estrus. These behavioral changes frequently develop gradually, sometimes over months, with owners attributing them to training issues, pain, or attitude problems before considering reproductive causes. The severity of behavioral changes often prompts veterinary evaluation that ultimately leads to tumor diagnosis.

Physical signs detectable on examination include ovarian enlargement that may reach remarkable proportions. Granulosa cell tumors commonly grow to baseball, softball, or even larger sizes, with some reaching dimensions of fifteen to twenty centimeters or more. Rectal palpation reveals an enlarged, typically firm ovary with irregular contours, while the contralateral ovary feels small and inactive due to hormonal suppression. Ultrasound examination characteristically shows multilocular structures with honeycomb or multicystic appearance in granulosa cell tumors. Physical changes related to hormone production may be visible, including enlarged clitoris in testosterone-producing tumors or mammary gland development in estrogen-producing cases.

Symptom progression in untreated ovarian tumors typically involves gradual tumor growth with intensifying hormonal effects. Behavioral changes that began as mild abnormalities become more pronounced and disruptive over time. Tumor size increases, sometimes dramatically over months to years. Abdominal discomfort may develop as tumors reach sufficient size to cause mechanical effects on surrounding structures. The contralateral ovary remains suppressed throughout tumor growth, with prolonged suppression potentially delaying recovery even after tumor removal. Rare malignant tumors may show additional symptoms related to metastatic spread including weight loss, decreased appetite, or signs referable to specifically affected organs.

Emergency symptoms directly related to ovarian tumors are uncommon but may occur in specific circumstances. Acute colic signs can develop if large tumors undergo torsion, cutting off blood supply and causing sudden severe pain. Tumor rupture or hemorrhage within rapidly growing masses may cause acute abdominal pain and signs of internal bleeding. Aggressive behavior from testosterone-producing tumors can escalate to dangerous levels posing immediate risk to handlers or other animals. While most ovarian tumors follow slowly progressive courses, any sudden deterioration in a mare with known or suspected ovarian tumor warrants urgent veterinary evaluation.

Physical examination for suspected ovarian tumor begins with thorough history gathering and external assessment before proceeding to reproductive tract evaluation. Behavior description provided by owners offers valuable diagnostic clues, with patterns of aggression, constant estrus, or absent cycling suggesting specific tumor hormone profiles. External examination may reveal physical changes associated with hormone production including clitoral enlargement, mammary development, or masculine neck conformation. General health assessment evaluates for any signs suggesting malignancy or metastatic spread, though such findings are uncommon. Careful observation of the mare's demeanor during handling often demonstrates the behavioral abnormalities that prompted examination.

Diagnostic testing for ovarian tumors combines reproductive tract assessment with hormone profiling and imaging studies. Transrectal palpation provides initial assessment of ovarian size, shape, and texture, typically revealing unilateral enlargement with contralateral ovary smallness. Hormone analysis plays a crucial diagnostic role, with specific patterns strongly suggesting particular tumor types. Elevated testosterone and inhibin with low or undetectable progesterone characterizes most granulosa cell tumors, while anti-Mullerian hormone elevation provides additional diagnostic confirmation. Estrogen levels vary depending on tumor hormone production profile. Complete blood count and serum chemistry panels screen for systemic effects and evaluate overall health in preparation for potential surgery.

Advanced diagnostic imaging significantly enhances ovarian tumor evaluation and surgical planning. Transrectal ultrasound examination reveals characteristic tumor architecture, with granulosa cell tumors typically showing multicystic or honeycomb internal patterns that differ markedly from normal ovarian structure or simple fluid accumulation. Tumor size can be accurately measured, guiding decisions about surgical approach. The contralateral ovary's small, inactive appearance supports diagnosis. Transabdominal ultrasound may provide additional visualization for very large tumors. Advanced imaging including CT or MRI is rarely necessary but may be considered when staging malignant tumors or evaluating suspected metastatic disease.

Differential diagnosis for ovarian tumors includes several conditions causing ovarian enlargement or behavioral changes in mares. Anovulatory hemorrhagic follicles and ovarian hematomas produce ovarian enlargement but differ in ultrasound appearance and typically resolve spontaneously. Ovarian abscesses cause enlargement with fever and inflammatory signs usually absent with tumors. Large physiologic structures including follicles and corpora lutea may occasionally reach sizes raising tumor suspicion, but these follow normal cycling patterns. Behavioral changes similar to hormone-producing tumors can result from exogenous hormone administration, adrenal disorders, or rarely pituitary dysfunction. Histopathologic examination of surgically removed tissue provides definitive tumor type diagnosis, important for prognosis and understanding individual tumor biology.

Emergency treatment for ovarian tumor complications addresses acute presentations requiring immediate intervention. Torsion of a tumorous ovary causes severe colic requiring emergency surgical correction, with prompt intervention necessary to relieve pain and prevent ischemic damage. Acute hemorrhage from tumor rupture or internal bleeding necessitates stabilization with intravenous fluids and potentially blood products before surgical intervention. Dangerous aggressive behavior may require immediate chemical restraint to ensure handler safety while diagnostic workup proceeds. These emergency scenarios are uncommon but require recognition and rapid response when they occur.

Medical management options for ovarian tumors are limited, as definitive treatment requires surgical removal in nearly all cases. No chemotherapy protocols have demonstrated efficacy for equine ovarian tumors, and hormonal suppression therapy does not eliminate tumor tissue. GnRH agonists may theoretically reduce hormone production from some tumors but do not address the underlying neoplasm. Medical management therefore focuses on controlling symptoms and preparing patients for surgery rather than treating tumors directly. Behavioral management through appropriate housing and handling protocols may be necessary while awaiting surgery to prevent injury from aggressive behavior.

Surgical removal of the affected ovary represents the definitive and usually curative treatment for ovarian tumors. Unilateral ovariectomy can be performed through standing flank approach under sedation and local anesthesia for tumors of moderate size, offering advantages of reduced anesthetic risk and faster recovery. Large tumors may require ventral midline celiotomy under general anesthesia, providing better exposure for removal and examination of other abdominal structures. Laparoscopic approaches offer minimally invasive options for selected cases, though tumor size often limits applicability. Surgical technique considerations include careful handling to prevent tumor rupture and thorough hemostasis given the highly vascular nature of many ovarian tumors.

Supportive care following ovariectomy addresses immediate post-operative needs and prepares the mare for return to function. Pain management using appropriate analgesics ensures comfort during initial recovery. Antimicrobial therapy may be administered prophylactically or therapeutically depending on surgical approach and contamination concerns. Incision care follows standard surgical wound management protocols appropriate to the specific approach used. Nutritional support maintains body condition during recovery, with return to normal feeding as gastrointestinal function normalizes. Stall rest during initial healing transitions to small paddock turnout and progressively increasing activity as recovery proceeds.

Rehabilitation and return to work following ovarian tumor removal follows timelines determined by surgical approach and individual recovery. Mares undergoing standing flank ovariectomy typically require two to four weeks of limited activity before gradual return to work. Ventral midline surgery necessitates longer recovery periods of six to eight weeks before resuming athletic activities. Reproductive recovery involves waiting for the contralateral ovary to resume normal function, which typically occurs within one to twelve months after surgery depending on the duration of suppression. Serial reproductive examinations track return of normal cyclicity and guide breeding timing for mares intended for reproduction.

Treatment decision factors include tumor type confirmation, mare value and intended use, and practical considerations regarding surgery. Nearly all granulosa cell tumors warrant surgical removal given their excellent prognosis and negative effects on fertility and behavior if left untreated. Rare malignant tumors require careful discussion of prognosis and potential additional treatments. Mare age, overall health, and anesthetic risk assessment influence surgical approach recommendations. Economic factors may impact decision-making for less valuable mares, though improved quality of life and restored usefulness often justify surgical costs. Owner goals regarding breeding versus performance use may influence surgical timing but rarely affect the fundamental recommendation for tumor removal.

Recovery timeline following ovarian tumor removal varies based on surgical approach, tumor characteristics, and individual mare factors. Initial surgical recovery requires one to two weeks of relative rest with incision monitoring and pain management. Standing flank ovariectomy patients often return to light work within three to four weeks, while mares undergoing ventral midline surgery need six to eight weeks before resuming ridden exercise. Complete reproductive recovery takes considerably longer, with the suppressed contralateral ovary requiring time to resume normal function. Most mares show return of estrous cycling within one to four months following surgery, though some individuals require up to twelve months for complete hormonal normalization.

Post-treatment care and monitoring encompass both surgical recovery and reproductive function assessment. Incision sites require daily monitoring for swelling, discharge, or dehiscence during the first two weeks. Suture or staple removal occurs at approximately ten to fourteen days for skin closures. Serial hormone testing confirms declining tumor-associated hormone levels, with testosterone and inhibin returning to normal ranges within weeks of granulosa cell tumor removal. Reproductive examinations track contralateral ovary reactivation, with follicular development and eventually ovulation indicating return of normal function. Documentation of regular estrous cycles over several months confirms complete reproductive recovery.

Prognosis factors influencing recovery outcomes include tumor type, duration of contralateral ovary suppression, and surgical complications. Granulosa cell tumors carry excellent prognosis, with greater than ninety percent of mares returning to normal reproductive function following uncomplicated surgery. Malignant tumor types carry more guarded prognoses depending on presence and extent of metastatic disease. Prolonged ovarian suppression before diagnosis may delay contralateral ovary recovery, with some mares requiring extended periods before resuming normal cycling. Surgical complications including infection, hemorrhage, or adhesion formation can impact both immediate recovery and long-term outcomes. Overall, most mares recover uneventfully and return to their intended use.

Long-term fertility outlook for mares following ovarian tumor removal is generally favorable. The remaining ovary compensates effectively for the removed organ, producing follicles and corpora lutea sufficient for normal reproduction. Studies demonstrate conception rates comparable to normal mares within one to two years following surgery in most cases. Some mares conceive on their first breeding cycle after return of normal ovarian function. Occasional individuals show persistent subfertility, potentially related to prolonged abnormal hormone exposure or subtle contralateral ovary changes from extended suppression. Mares intended for breeding programs should have normal cycling confirmed over several cycles before breeding attempts, optimizing chances for successful conception.

Management practices for ovarian tumor prevention remain limited given the poorly understood etiology of these conditions. Since no specific causative factors have been identified, targeted prevention protocols cannot be developed. Regular reproductive examination represents the most effective management strategy, allowing early tumor detection before significant growth or hormonal effects develop. Annual or biannual reproductive ultrasound examinations provide opportunities to identify developing ovarian abnormalities at early, easily treatable stages. Breeding managers should incorporate ovarian assessment into routine pre-breeding evaluations, establishing baseline examinations that facilitate future comparisons.

Nutritional considerations specific to ovarian tumor prevention have not been established. Balanced diets supporting overall health remain appropriate, as general wellness contributes to optimal immune function that may help suppress early neoplastic changes. No specific nutrients or supplements have demonstrated protective effects against ovarian tumor development. Avoiding nutritional deficiencies or excesses that could compromise overall health represents reasonable general practice. Maintaining appropriate body condition supports reproductive health broadly without specific tumor prevention mechanisms.

Exercise and conditioning contributions to ovarian tumor prevention remain undefined. Regular appropriate exercise supporting overall mare health may indirectly contribute to cancer resistance through optimized immune function, though this remains theoretical for ovarian tumors specifically. Neither high-level athletic training nor sedentary management has been associated with ovarian tumor risk. Exercise recommendations should focus on overall health benefits rather than tumor prevention specifically, with programs appropriate to individual mare use and fitness level.

Environmental factors potentially modifiable for ovarian tumor prevention have not been identified. Unlike some cancer types with known environmental triggers, equine ovarian tumors show no established associations with management conditions, chemical exposures, or housing situations. Reproductive hormone use for breeding management has not been linked to subsequent tumor development. General recommendations to minimize unnecessary medication exposure and provide quality living conditions support overall health without specific tumor prevention evidence.

Reproductive monitoring protocols offer the most practical approach to managing ovarian tumor risk through early detection rather than true prevention. Pre-breeding examinations should include bilateral ovarian assessment, documenting normal size and structure. Any noted ovarian asymmetry or abnormal texture warrants follow-up examination or immediate investigation depending on severity. Mares showing unexplained behavioral changes should receive reproductive evaluation including ovarian assessment. Owners should be educated about ovarian tumor signs, prompting veterinary consultation when suggestive changes develop. This surveillance approach ensures most tumors are detected early when treatment is straightforward and outcomes are optimal.

Daily management adjustments for mares diagnosed with ovarian tumors depend on tumor effects and timing relative to planned treatment. Mares with significant behavioral changes require modified handling protocols to ensure safety, with aggressive mares potentially requiring individual housing away from other horses. Handling procedures should minimize confrontational situations and ensure adequate personnel with appropriate expertise. For mares showing constant estrus behavior, management should anticipate distraction and reduced focus during training or handling sessions. Feed and water provision continue normally, with attention to maintaining body condition during the period awaiting surgery.

Housing and turnout considerations for mares with hormone-producing ovarian tumors address both mare welfare and safety concerns. Aggressive mares with testosterone-producing tumors may require individual turnout to prevent injury to pasturemates, particularly if showing stallion-like behavior toward mares. Even with individual turnout, fence line contact with other horses may provoke dangerous behavior requiring complete visual and physical separation. Mares with estrus-type behavior may be manageable in group settings but may cause herd disruption through constant soliciting of attention. Following surgical treatment, gradual reintroduction to group housing can proceed as behavior normalizes.

Exercise modifications during the period of ovarian tumor diagnosis through treatment depend on behavioral safety and general health status. Mares with mild behavioral changes may continue normal work if handlers can safely manage their behavior. Significant aggression or unpredictable behavior precludes safe riding or ground work until surgical treatment restores normal temperament. Following surgery, exercise restrictions appropriate to the surgical approach apply during healing. Return to full work proceeds as recovery allows, with attention to any persistent behavioral quirks that may require address through training once hormonal causes have been eliminated.

Monitoring and ongoing care requirements extend throughout the diagnostic, treatment, and recovery periods. Pre-surgical monitoring documents tumor characteristics, hormone profiles, and behavioral patterns providing baseline for post-surgical comparison. Following surgery, observation for complications, hormone normalization, and behavioral improvement guides recovery management. Long-term monitoring for mares with malignant tumor types includes periodic examinations and imaging to detect potential recurrence or metastatic disease. Mares returning to breeding programs require documentation of normal reproductive cycles before breeding attempts. Comprehensive records support ongoing care decisions and provide valuable information should any future reproductive issues arise.

Quality of life and use considerations for mares with ovarian tumors improve dramatically following successful surgical treatment. Pre-surgical quality of life may be significantly impacted by behavioral changes that prevent normal social interactions and preclude intended use whether breeding or performance. Successful tumor removal typically restores normal behavior within weeks to months, allowing mares to return to their previous roles. Mares that cannot undergo surgery due to medical contraindications or economic constraints face ongoing quality of life challenges from persistent behavioral abnormalities. For such mares, management modifications to maintain safety and basic welfare become long-term considerations. The generally excellent surgical outcomes support strong recommendation for ovariectomy whenever feasible.

Ovarian tumors can develop in mares of any breed without clear breed predisposition based on current evidence. While individual studies have occasionally suggested possible increased incidence in certain breeds, these findings have not been consistently replicated and may reflect study population biases rather than true breed susceptibility. Draft breeds, light horse breeds, and pony breeds all experience ovarian tumors at comparable rates when population numbers are considered. Arabians, Quarter Horses, Thoroughbreds, and Warmbloods appear in case reports roughly proportional to their representation in the general horse population. No breed can be considered either immune to or specifically at risk for ovarian tumor development.

Use and discipline appear unrelated to ovarian tumor occurrence, with affected mares identified across all uses including breeding, pleasure riding, competitive disciplines, and retired status. Neither intensive breeding management nor complete reproductive inactivity has been associated with increased tumor risk. Performance demands do not influence tumor development, though behavioral effects of hormone-producing tumors often first draw attention in competition settings where behavioral changes impact performance. Mares used as embryo donors or oocyte sources do not show elevated tumor rates despite intensive reproductive manipulation. The apparent randomness of tumor occurrence across uses and disciplines suggests that activity-related factors do not significantly influence risk.

Genetic testing and breeding recommendations for ovarian tumors cannot currently be formulated given the absence of identified genetic factors. The sporadic occurrence of ovarian tumors across breeds and families does not support avoidance of specific breeding combinations. Mares successfully treated for benign tumors should not be excluded from breeding programs based on tumor history, as no evidence suggests increased risk in offspring. Maintaining records of ovarian tumor occurrence within breeding populations may eventually reveal patterns worthy of investigation, though current data does not support genetic screening recommendations. The most practical approach remains regular reproductive monitoring to detect any tumors early regardless of breeding or family history.

Commonly co-occurring conditions with ovarian tumors include hormonal imbalances caused by the tumors themselves, which then produce secondary effects throughout the body. Mammary gland enlargement may develop in mares with estrogen-producing tumors, sometimes progressing to milk production. Laminitis occasionally occurs in association with hormonal disruption, though this remains uncommon. Ovarian atrophy of the contralateral ovary represents a consistent finding resulting from tumor hormone feedback suppression rather than a true separate condition. Behavioral disorders associated with hormone production may persist after tumor removal in rare cases, potentially requiring additional management attention.

Conditions presenting with similar symptoms to ovarian tumors require careful differentiation. Behavioral changes resembling hormone-producing tumor effects can result from adrenal gland tumors or dysfunction, pituitary disorders, or exogenous hormone exposure. Ovarian cysts may cause enlarged ovary findings but typically show different ultrasound characteristics and normal hormone profiles. Ovarian hematoma produces enlargement that can initially raise tumor suspicion but usually resolves spontaneously and lacks hormonal effects. Pyometra and other uterine conditions may cause some behavioral changes attributed to reproductive abnormalities. Anestrus from non-tumor causes including seasonality, poor body condition, or lactation must be distinguished from tumor-induced reproductive quiescence.

Potential complications of ovarian tumors include both direct tumor effects and treatment-related concerns. Tumor growth may eventually cause abdominal discomfort or rarely organ compromise if masses reach sufficient size. Torsion of large tumorous ovaries causes acute colic requiring emergency surgery. Rare malignant tumors carry risks of metastatic spread to other abdominal organs, lungs, or other sites. Surgical complications including hemorrhage, infection, and adhesion formation can occur with ovariectomy. Prolonged hormonal suppression of the contralateral ovary may delay post-surgical return to fertility. Persistent behavioral abnormalities following surgery occasionally require additional management attention. Despite these potential issues, most mares experience uncomplicated tumor removal with complete return to normal function.