[Five case reports on granulosa cell tumors in cattle with practical information on diagnosis and possible progression]. / Fünf Fallberichte zum Granulosazelltumor beim Rind mit praktischen Hinweisen zur Diagnostik und zum möglichen Verlauf.

INTRODUCTION: Five cases of ovarian tumors (granulosa cell tumors) in cattle are presented from the patient load of the Vetsuisse University of Zurich and Bern. The aim of this work was to demonstrate the variable development of the illness and to indicate diagnostic and therapeutic possibilities to the practicing veterinarians. Case 1 shows bilateral appearance and the development of malignancy and metastases. The main symptoms in case 2 were the development of the mammary gland in a juvenile animal and the behavior modification due to a hormonal imbalance. The cases 3, 4 and 5 underwent surgery, case 4 restarted reproductive activity resulting in five subsequent pregnancies. The initial presumption is a result of a gynecological including ultrasonographic examination and can be verified by the analysis of Müllerian Inhibiting Hormone in serum. The decision to perform surgery should be done rapidly, as normal fertility can be achieved if the tumor is located unilaterally. Tumor growth and potential malignancy can provoke fatal health issues and also make it impossible to use meat of these animals for consumption.

INTRODUCTION: Cinq cas de tumeurs ovariennes (tumeurs des cellules de la granulosa) chez les bovins sont présentés à partir de la patientèle de l'Université Vetsuisse de Zurich et de Berne. Le but de ce travail était de montrer l'évolution variable de la maladie et d'indiquer les possibilités diagnostiques et thérapeutiques aux vétérinaires praticiens. Le cas 1 montre la possibilité d'une apparition bilatérale avec développement d'une tumeur maligne et de métastases. Les principaux symptômes du cas 2 étaient le développement de la glande mammaire chez un animal juvénile et la modification du comportement due à un déséquilibre hormonal. Les cas 3, 4 et 5 ont subi une intervention chirurgicale, le cas 4 a repris une activité de reproduction avec cinq gestations ultérieures. La présomption initiale résulte d'un examen gynécologique et peut être vérifiée par l'analyse de l'hormone anti-müllérienne dans le sérum. La décision d'opérer doit être prise rapidement, car une intervention chirurgicale pour enlever l'ovaire atteint peut, dans l'idéal, permettre une reprise de l'activité de reproduction. La croissance de la tumeur et la malignité potentielle peuvent provoquer des problèmes de santé fatals et rendre la viande de ces animaux impropre à la consommation.

Successful intra-abdominal resection of a 24 kg ovarian granulosa cell tumor in a Warmblood mare.

Background: Granulosa cell tumors (GCTs) are the most common ovarian tumors in mares. The classical presentation of a GCT is a unilaterally enlarged ovary appearing as a multicystic honeycomb mass. In rare cases, GCTs cause hemoperitoneum as a result of the rapid growth of the tumor. The clinical diagnosis of GCT is usually based on history, rectal examination, ultrasonographic examination, and serum hormone analysis, and surgical removal of the affected ovary is the treatment of choice. The different surgical approaches are based on the dimension of the GCT. Case Description: A 7-year-old mare was referred to the department for horses due to suspicion of a large colon impaction. The mare presented with clinical signs of colic, fever, and signs of hypovolemic shock. Rectal and ultrasonographic examination showed hemoperitoneum and a honey-comb mass within the abdomen, and a GCT as the cause of an acute hemoperitoneum was diagnosed based on the serum level of anti-Müllerian hormone. After stabilization of the mare, the GCT was removed through a ventral midline incision. Because of the enormous dimensions of the GCT, intra-abdominal partial resection of the tumor using a tenotomy knife was necessary to exteriorize the ovarian pedicle. At 3 months follow-up, the mare was ridden for her intended use. Conclusion: This report provides an approach to an uncommon case of a very large and heavy GCT.

Clinical and ultrasonographic findings of ovarian tumours in bitches: A retrospective study.

A retrospective study was carried out to investigate incidence, clinical signs and ultrasonographic findings of ovarian tumours in a population of dogs referred to the Veterinary Teaching Hospital of the University of Perugia (Italy) and Anicura Tyrus Veterinary Clinic (Terni, Italy). The period of study ranged from January 2005 to December 2021. A total of 1910 dogs were affected by neoplasia but only 35 of them (1.8%), of different breeds and ages, were found to have ovarian tumours. Ultrasound of the ovaries was performed based on clinical signs; the diagnosis was achieved after ultrasound findings prompted ovariohysterectomy and ovarian pathologic evaluation In our study, the age of bitches affected by ovarian neoplasia ranged from 3 to 20 years (mean 9.6 ± 3.8). The histopathological findings of ovarian masses identified 16 granulosa cell tumours (GCT) (46%), 7 adenomas (20%), 5 adenocarcinomas (14%), 2 teratomas (6%), 1 leiomyoma (3%), 1 luteoma (3%), 1 tecoma (3%), 1 dysgerminoma (3%), and 1 haemangiosarcoma (3%). In particular, with respect to clinical signs, 69% of bitches showed abnormalities of estrus cycle (short interestral interval, persistent estrus, prolonged interestral interval). The other main clinical signs included abdominal distention, palpable abdominal mass, vulvovaginal discharge, polyuria/polydipsia, mammary masses. When present, the laboratory abnormalities were slight anemia and leucocytosis with neutrophilia. The tumours were ultrasonographically classified as mainly solid: 12/35 (34%) (1 adenoma, 4 adenocarcinomas, 1 dysgerminoma, 1 haemangiosarcoma, 1 leyomioma, 1 luteoma, 1 GCT, 1 tecoma, 1 teratoma); solid with cystic component 13/35 (37%) (9 GCT, 2 Adenomas, 1 adenocarcinoma, 1 teratoma); and mainly cystic 10/35 (29%) (6 GCTs, 4 adenomas). In our study, the ultrasound examination allowed us to suspect ovarian neoplasia in asymptomatic subjects referred for breeding management or for preventive health check. On the basis of our data, we proposed to perform a complete periodic examination of the reproductive system once a year from 6 years. Nevertheless, the presence of ovarian neoplasms found in young subjects, during breeding management, suggest including routine ultrasound examination of the reproductive tract.

Granulosa cell tumour in a llama (Lama glama).

Hormonally active tumours are characterized by production and secretion of hormones, irrespective of endogenous feedback mechanisms. An adult llama had exuberant oestrous behaviour, infertility, elevated concentrations of oestradiol and a large ovarian mass. Necropsy revealed the presence of two large abdominal masses, one effacing the right ovary and one in the mesocolon. Considering the clinical and histopathological findings, we conclude that the llama was affected by a granulosa cell tumour. The case suggests that granulosa cell tumours in camelids are hormonally active, and the clinical presentation resembles that of other large animal species. To our knowledge, this is the first case report of an oestrogen-producing, metastatic granulosa cell tumour in a llama.

Comparison of anti-Müllerian hormone and inhibin immunolabeling in canine and equine granulosa cell tumors.

Granulosa cell tumors (GCTs) are common ovarian neoplasms in the mare and bitch that can be challenging to diagnose on histopathology. Inhibin has long been the standard immunohistochemical (IHC) marker for GCTs; however, anti-Müllerian hormone (AMH) has not been evaluated widely as an IHC marker in the bitch and mare. We compared the efficacy of AMH and inhibin as IHC markers in canine and equine GCTs. We selected retrospectively 18 equine and 15 canine cases. All equine tumors were dominated by a cystic pattern; canine tumors often had solid patterns. Both inhibin and AMH had similar punctate cytoplasmic patterns of immunolabeling, although labeling intensity was variable; distribution and intensity of labeling were unrelated to the histomorphologic pattern. Labeling for AMH occurred in 12 of 15 canine and 18 of 18 equine cases. Labeling for inhibin occurred in 15 of 15 canine and 18 of 18 equine cases. AMH in equine GCTs often had stronger immunolabeling than inhibin, and granulosa cells were labeled more extensively. Inhibin and AMH performed comparably in bitches, but AMH had more diffuse immunolabeling than inhibin in mares.

Ovarian granulosa cell tumor in a Persian cat: Case report from Tripoli, Libya.

Background: Ovarian granulosa cell tumors (GCTs) are common neoplasms in domestic animals that originate from the sex-cord stromal cells of the ovary. The aim of the present paper was to report a case of ovarian GCT in a 5-year-old Persian female cat and to describe the histopathological pattern of this tumor. Case Description: The cat was brought for a routine diagnostic examination for pregnancy at Albaittar clinic in Tripoli, Libya with a history of 1 month mating before it was brought to the clinic for investigation of progressive behavioral changes. The cat external examination showed noticeable enlargement in the abdomen that was potentially suspected of pregnancy; however, the abdominal ultrasonography showed a great mass located on the right ovary. A therapeutic ovariohysterectomy was performed. The cat's clinical signs resolved, 6 months later it was diagnosed with a mass on the right kidney suspected as metastasis and one week later the cat died. Conclusion: In this case, macroscopic and microscopic studies are discussed and histopathological examination confirmed ovarian GCT with cystic endometrial hyperplasia and suspected metastasis in one kidney.

Characterization of an incipient granulosa cell tumour in a Holstein cow: Steroid hormone receptors and coregulators expression.

The objective of this study was to describe a case of a granulosa cell tumour (GCT) of incipient formation and to characterize it by its immunohistochemical pattern and hormonal profile. The case presented corresponds to a 7-year-old Holstein cow without reproductive disorders. No alterations were observed at rectal palpation, neither in the ultrasonography nor in the hormonal profile. A GCT concomitant with normal follicular development was diagnosed. Through a panel of immunohistochemical markers, a highly differentiated pattern could be determined in the GCT, which preserves the expression of steroid receptors (ESR1, ESR2 and PR) typical of granulosa cells, but does not express the enzymes for the synthesis of androgens (CYP17A1) and oestrogens (CYP19A1). In addition, the expression of co-regulators of steroid hormone receptors and neuroendocrine markers was described for the first time in a GCT in cattle. These results increase the information about GCTs in cattle before the ovarian function is compromised.

Immunohistochemical and Morphological Features of Bovine Granulosa Cell Tumours in Relation to Growth Pattern and Folliculogenesis.

Granulosa cell tumours (GCTs) are the most common type of bovine ovarian neoplasm. We describe the morphological and immunohistochemical features of GCTs (n = 26) and a thecoma (n = 1) using antibodies to cytokeratin AE1/AE3, vimentin, desmin, nectin-4, anti-Müllerian hormone (AMH), inhibin α, c-erbB-2 oncoprotein and proliferating cell nuclear antigen. The results indicate that, based on the expression similarity of AE1/AE3 and inhibin α, the macrofollicular growth pattern of GCTs derives from highly differentiated granulosa cells (GCs), the Graafian follicle or early atretic follicle. The trabecular growth pattern of GCTs is inferred to be derived from GCs of the atretic follicle in mature animals. AMH is a useful marker for diagnosing bovine sex cord-stromal tumours because it was expressed in all GCT cases and in the single case of thecoma.

Immunohistochemical expression of HER - 2 and Ki - 67 in granulosa cell tumor in bitches.

Granulosa cell tumour, an ovarian neoplasm of stromal origin, is an important tumour related to oestrogenic dominance syndrome and cystic endometrial hyperplasia-pyometra complex. In order to analyse ovarian tumour´s malignant potential, immunohistochemical markers can be used, such as anti-HER2 and anti-Ki-67. The aim of this study was to evaluate the expression of immunohistochemical markers HER-2 and Ki-67 in granulosa cell tumour from bitches´ ovaries. In HER-2 immunomarker analysis using the HercepTest® method, most tumours were classified as 2+ (moderate labelling). Concerning Ki-67 immunomarker, only one case was described as having a high proliferative index. An association was found between immunostained cell percentage by anti-HER-2 antibodies and high pleomorphism, represented by the pattern of follicular/trabecular tumour arrangement. There was no correlation between anti-Ki-67 and anti-HER-2 antibody immunostaining intensities, probably due to only one case with a high Ki-67 index. With an effective protocol for HER-2 and Ki-67 immunohistochemical identification in granulosa cell tumours in bitches, it was possible to characterize this neoplasm proliferation profile.

Granulosa cell tumor in 8 African pygmy hedgehogs (Atelerix albiventris).

A retrospective study involving eight African pygmy hedgehogs histopathologically diagnosed with granulosa cell tumors was conducted. The age at onset was 2.2-4.5 years, with a median age of 3.6 years. The most common clinical signs were hematuria and abdominal distension, which were observed in >50% cases. Exploratory laparotomy was performed in all cases, and ovariohysterectomy or excision of the abdominal mass was performed. Patients with only hematuria survived for >250 days after surgery, whereas those with initial ascites showed recurrence of ascites or tumor growth and survived for approximately 130 days after surgery. Intraperitoneal injection of carboplatin was performed in three recurrent cases. In one of these three cases, the tumor mass disappeared. Hence, carboplatin can be considered a potential antineoplastic drug for the treatment of granulosa cell tumors.

Active immunisation against GnRH as treatment for unilateral granulosa theca cell tumour in mares.

BACKGROUND: Stallion-like or aggressive behaviour in mares affected by unilateral granulosa theca cell tumour (GTCT) is well-known, but use of a GnRH-vaccine as an alternative to surgical removal of the neoplastic ovary has not been investigated. OBJECTIVES: To determine the effect of immunisation against GnRH on ovarian size, testosterone concentration, Anti-Müllerian hormone (AMH) concentration, and owner-reported behaviour in four mares affected by unilateral GTCT. STUDY DESIGN: Retrospective case report. METHODS: A presumptive diagnosis of GTCT was made in four mares based on clinical signs, behavioural changes, transrectal palpation, and ultrasonography. All mares were vaccinated twice with the GnRH-vaccine Improvac® on day 0 and on day 13-33. Further booster vaccinations were administered if aggressive behaviour recurred between days 15 and 498. Before and parallel to the vaccinations, serum levels of oestradiol, progesterone (P4), testosterone, and AMH were evaluated and transrectal ultrasonography was performed. RESULTS: In all horses, analysis of serum levels of oestradiol, progesterone, testosterone, and AMH confirmed the clinical diagnosis of GTCT. Serum levels of testosterone dropped to baseline levels following the first two of three vaccination in all mares. In addition, AMH serum values decreased shortly after the second vaccination in three of four mares, and in one of the four mares returned to baseline levels. No further GTCT linked behaviour was reported by the owners and the affected ovaries diminished in size in all four cases. MAIN LIMITATIONS: This report is a case series with a limited number of animals, no controls and no standardised immunisation protocol. CONCLUSIONS: Repeated vaccinations with the GnRH-vaccine Improvac® mitigated owner-reported behavioural abnormalities and stopped tumour growth in four mares affected by unilateral GTCT over the entire observation period which extends to 7 years in one mare.

Equine granulosa cell tumours among other ovarian conditions: Diagnostic challenges.

BACKGROUND: Granulosa cell tumours (GCT) are the most common ovarian tumours in mares. While the classical presentation may not represent diagnostic challenges, diagnosis is not easy in the early stages. OBJECTIVES: Illustrate the variability in the presentation and serum biomarkers associated with ovarian abnormalities in the mare. STUDY DESIGN: Retrospective case series. METHODS: Nonclassical cases of GCTs and other ovarian conditions were identified and behaviour, GCT endocrine results, palpation and ultrasonographic findings are described and the diagnostic value of each is discussed. RESULTS: Mares in this case series with GCTs had been presenting clinical signs ranging from no behavioural changes to behaviours including aggression, stallion-like and inability to work under saddle. Hormonal profiles of endocrinologically functional GCTs can be erratic and unpredictable. The clinical form and ultrasonographic appearance may also vary with time from an initially enlarged/anovulatory follicular structure that later develops a multicystic 'honeycomb' appearance. Mares with GCTs can also present with persistent anovulatory follicles or apparent luteal tissue that are unresponsive to treatment. If both ovaries are of relatively normal size and symmetry, but hormonal biomarkers are markedly increased (AMH >10 ng/mL, inhibin B and/or testosterone >100 pg/mL; 0.37 nmol/L), it is likely that a functional GCT is present. Still, it can be a challenge to decide which ovary to remove. Post-surgical endocrine testing can be helpful, especially if histopathology is not performed or a GCT is not found. MAIN LIMITATIONS: Cases limited to 14. CONCLUSIONS: Granulosa cell tumours present with a wide variety of clinical signs that do not fit what is commonly described as 'classic'. Only if AMH, testosterone and inhibin B concentrations are markedly increased, and there is an abnormally enlarged ovary, the diagnosis of a GCT is more confident. In the presence of normal size ovaries, normal hormonal biomarkers and abnormal behaviour, it is more likely that the ovaries are not involved.

A retrospective analysis on the outcome of 18 dogs with malignant ovarian tumours.

Little evidence is available regarding the prognosis of dogs with malignant ovarian tumours. The objective of this retrospective study was to describe the outcomes and determine the prognostic factors for dogs with malignant ovarian tumours following treatment, including surgery with or without adjuvant therapy. Eighteen dogs were studied, their median age was 12 years (range: 7-15 years), and their median body weight was 6.9 kg (range: 2.3-17.8 kg). Following histopathologic diagnoses revealed that granulosa cell tumour was the most common type (n = 9), followed by dysgerminoma (n = 5), and adenocarcinoma (n = 4). Eleven dogs had surgery alone. Seven dogs had surgery with adjuvant therapy, including chemotherapy and/or radiotherapy. The median survival time (ST) was 1009 days when only deaths owing to the ovarian tumours were considered, and predictors of median ST were T-category (≥ T3, 443 days vs ≤ T2, 1474 days; P = .002), presence of metastatic disease (present, 391 days vs absent, 1474 days; P < .001) and lymphovascular space invasion (present, 428 days vs absent, 1474 days; P = .003) in a univariate analysis. Median ST in dogs with granulosa cell tumour seemed longer than in dogs with dysgerminoma and adenocarcinoma, although the difference was statistically insignificant (1474 days vs 458 days, respectively; P = .10). Considering the good prognosis, aggressive treatment can be recommended for dogs with malignant ovarian tumours, especially early-stage cases. Despite metastasis being present at diagnosis, half of the dogs with metastasis survived for more than 1 year.

Ovarian histopathology, pre- and post-operative endocrinological analysis and behavior alterations in 27 mares undergoing bilateral standing laparoscopic ovariectomy.

Determining if ovariectomy will abolish unwanted behaviors can be challenging in mares without ultrasonographic ovarian abnormalities and/or endocrine values not consistent with a granulosa cell tumor. The objective of the study was to identify mares that have a positive improvement in unwanted behaviors after elective standing laparoscopic ovariectomy and to determine if the change is associated with any pre- and post-operative endocrine profiles and/or with ovarian histological findings. During the study period 27 mares underwent a bilateral standing laparoscopic ovariectomy. Pre- and post-operative questionnaires and endocrine profiles, along with ovarian histopathology were performed and data were analyzed. Eighty-nine percent of clients were satisfied with the change in behavior after surgery. There were no significant associations between specific elevated hormones or absent luteal tissue with any specific unwanted behaviors. Pre-operative endocrine values were not predictive of post-operative owner satisfaction but bilateral ovariectomy for the treatment of unwanted behaviors in mares had a high likelihood of achieving owner satisfaction.

Histopathologie ovarienne, analyse endocrinienne pré- et post-opération et modifications du comportement chez 27 juments soumises à une ovariectomie bilatérale laparoscopique en position debout. Déterminer si une ovariectomie éliminera les comportements non-désirés peut représenter un défi chez les juments sans anomalie ovarienne détectable par échographie et/ou ayant des valeurs endocrines non cohérentes avec une tumeur des cellules de la granulosa. L'objectif de la présente étude était d'identifier les juments avec une amélioration positive des comportements non-désirés à la suite d'une ovariectomie élective par laparoscopie en position debout et de déterminer si le changement était associé avec un quelconque profil endocrinien pré- et post-opération et/ou avec des trouvailles histologiques dans les ovaires. Durant la période d'étude 27 juments ont été soumises à une ovariectomie laparoscopique bilatérale en position debout. Des questionnaires pré- et post-opération ainsi que des profils endocriniens et des analyses histopathologiques des ovaires furent réalisés et les données analysées. Quatre-vingt-neuf pourcents des clients étaient satisfaits avec le changement dans le comportement après la chirurgie. Il n'y avait pas d'association significative entre des niveaux élevés d'hormones spécifiques ou l'absence de tissu lutéal et des comportements non-désirés spécifiques. Les valeurs endocrines pré-opération n'étaient pas prédictives de la satisfaction post-opération des propriétaires mais l'ovariectomie bilatérale pour le traitement de comportements non-désirés chez les juments avait un grand potentiel d'obtenir la satisfaction du propriétaire.(Traduit par Dr Serge Messier).

Bilateral granulosa cell tumor in a cycling mare.

A 16-year-old Oldenburg mare was evaluated for stallion-like behavior. The mare had given birth to 2 foals previously. Transrectal palpation revealed bilaterally enlarged ovaries with no palpable ovulation fossa. Ultrasound examination showed both ovaries to have small follicles giving a honeycomb appearance, concurrent with a single large cystic structure in the left ovary (10.2 cm diameter). Serum Anti-Müllerian hormone (AMH) was elevated (95.7 pmol/L), consistent with granulosa cell tumor (GCT). Both ovaries were removed via flank laparoscopy and were evaluated by histopathology, which confirmed bilateral GCT and concurrent presence of fresh luteal tissue, demonstrating the unusual presentation of bilateral granulosa cell tumor in a cycling mare.

Tumeur bilatérale de la granulosa chez une jument en cycle. Une jument Oldenburg âgée de 16 ans a été évaluée pour un comportement s'apparentant à celui d'un étalon. La jument avait précédemment donné naissance à deux poulains. La palpation transrectale a révélé des ovaires élargis bilatéralement sans fosse d'ovulation palpable. L'échographie a indiqué que les deux ovaires avaient de petits follicules à l'apparence de nid d'abeilles ainsi qu'une seule grande structure cystique dans l'ovaire gauche (diamètre de 10,2 cm). L'hormone antimllérienne (HAM) était élevée (95,7 pmol/L), conformément à une tumeur de la granulosa (TG). Les deux ovaires ont été enlevés par laparascopie du flanc et ils ont été évalués par histopathologie qui a confirmé les TG bilatérales et la présente concomitante de tissu lutéal frais, ce qui démontre la présentation inusitée des tumeurs granulosa bilatérales chez une jument en cycle.(Traduit par Isabelle Vallières).

Double ovarian tumour in the mare: Case report.

Ovarian tumours in mares represent 2.5% to 6% of the most frequent neoplasms found in the equine species, with a higher chance of benignity. This study aims to describe a case of two different tumours found in the same ovary of a mare that presented clinical signs of suppressed oestrous cycle during 5 years. After unilateral ovariectomy, the ovary was sent to the histopathology examination which determined a mixed tumour of granulosa cell and leiomyosarcoma. After treatment, the mare returned to oestrus and got pregnant in the next season.

Histopathological findings in the early diagnosis of granulosa cell tumour in bitches.

Granulosa cell tumour (GCT) is a majorly observed ovarian tumour in female dogs. It is essential to diagnose GCT in its initial phase before any symptoms occur, as histological and physiological differences may be observed based on the evolution of this neoplasia. This study aimed to analyse the anatomic histopathology of GCT in its initial stage, with findings of ovaries not yet with the suspicion of neoplasms in the Canis familiaris. A sample including 55 ovaries presented GCT in 40 female dogs. The histopathological analysis was performed considering the intensity of pleomorphism, vascularization and inflammatory infiltrate. Furthermore, we evaluated the mitoses count in 10 fields using 40× magnification. Out of the 40 animals evaluated, 62.5% (25/40) presented the tumour in only one ovary. The Call-Exner corpuscle was present in 65% (26/40) of the cases. The follicular histological pattern was present in 52.5% (21/40) of the animals. The presence of the Call-Exner bodies and the degree of tumour cell pleomorphism (p = 0.033) were associated. Moreover, the degree of vascularization and the intensity of the inflammatory infiltrate were also related (p = 0.001). In addition, there was a positive relationship between the increase in pleomorphism and the mean age of the animals (p = 0.044). This study confirmed that the appearance of this tumour may precede any clinical symptomatology. In this study, the most frequent histopathological pattern was the follicular. The characteristics of the granulosa cell tumour diagnosed early were poorly pleomorphic cells, low mitotic index and presence of Call-Exner body.

Anti-Muellerian hormone concentration in bitches with histopathologically diagnosed ovarian tumours and cysts.

Increased concentrations of Anti-Muellerian hormone (AMH) can indicate a granulosa cell tumour as shown in women, mares and cows. To investigate AMH to differentiate canine granulosa cell tumour from other ovarian pathologies, we evaluated the ovaries of 63 bitches. Blood serum samples were collected before surgery for AMH analysis. Ovaries were submitted for histopathological examination. Fourteen bitches showed normal ovaries. These bitches had AMH values between 0.12 and 0.99 ng/ml. In 20 bitches ovarian cysts i.e., follicular cysts (n = 8), corpora lutea cysts (n = 7), subsurface cysts (n = 5) were diagnosed. These dogs had AMH values of 0.11-2.09 ng/ml. Bitches with small luteinized follicular cysts had slightly higher AMH values than those without ovarian alteration. In 29 cases ovarian neoplasms i.e., granulosa cell tumour (n = 9), epithelial tumours (n = 16), dysgerminomas (n = 3) and one sarcoma were identified. Anti-Muellerian hormone values of bitches with an ovarian neoplasm except granulosa cell tumour ranged from 0.18 to 1.18 ng/ml. The AMH values of bitches with granulosa cell tumour ranged from 1.12 to ≤23 ng/ml and were significantly higher (p < .05) than in all of the other bitches. The cut-off of 0.99 ng/ml gave a sensitivity of 100% and a specificity of 94.44% to diagnose granulosa cell tumour. In conclusion, markedly elevated AMH concentrations in bitches are indicative for a granulosa cell tumour. However, negative testing does not rule out the existence of small one. Differentiation of GCT from luteinized follicular cysts may especially be difficult.