Sertoli cell tumours (SCTs) in dogs: Incidence profile, cytological and haematobiochemical findings from 19 cases

Introduction

The important genital tumours of male dogs encountered in clinical practice include testicular tumours and transmissible venereal tumours (TVTs). Testicular tumours comprise seminoma, sertoli cell tumour (SCT) or sustentacular cell tumour, and Leydig cell tumour. In addition to the testicular tumours which commonly present as a visible or palpable enlargement of one or both testicles, several non-neoplastic conditions such as congenital and developmental anomalies, inflammatory conditions such as orchitis, testicular hyperplasia, and other pathological changes such as haemorrhage and necrosis within the testicular tissue can also cause testicular enlargement in dogs. Nodtvedt et al. (2011) [8] stated that testicular tumours are the most common neoplasms in male dogs and Manuali et al. (2020) [7] reported a population incidence of 19.7%. TVT, on the other hand, is a contagious round cell neoplasm that primarily affects sexually active male and female dogs through coitus or direct contact with tumour-infected tissues (Subapriya et al., 2025) [12] . The authors recorded a population incidence of 11.31% for TVT in dogs in their study. Considering the etiology of testicular tumours, Quartuccio et al. (2012) [9] stated that although the exact etiology of testicular tumours remains unidentified, increasing age, breed-specific environmental conditions and cryptorchidism act as major risk factors. Sivasudharsan et al. (2017) [11] further stated that cryptorchidism significantly increases the risk of testicular tumour development, with cryptorchid dogs showing a higher likelihood of developing Sertoli cell tumours than seminomas. Clinically, SCTs typically present as unilateral enlargement of one or both testicles, with or without radiographic evidence of metastasis. According to Borbil and Catoi (2007) [2] , SCTs are almost always benign, with a metastasis rate of less than 10% and the regional lymph nodes being the most common metastatic sites. The primary sites of metastasis are iliac, sublumbar and pelvic lymph nodes, peritoneum and other abdominal organs [1] . Interestingly, SCTs are unique among canine testicular neoplasms as features of feminization are appreciable in the affected male dogs. The incidence of feminization increases from approximately 15% in scrotally located tumours to 70% in abdominally retained tumours and about one-fourth of dogs with SCT exhibiting feminization attract other male dogs, similar to a bitch in estrus (Borbil and Catoi, 2007) [2] . Herzog et al. (2023) [5] attributed the clinical manifestations of feminization seen in dogs with sertoli cell tumours such as bilaterally symmetrical alopecia of the trunk and flanks, inguinal hyperpigmentation, gynecomastia, pendulous prepuce, squamous metaplasia of the prostate and attraction shown by male dogs to hyperestrogenism arising from the secretory nature of SCTs. Testicular tumours should be thoroughly evaluated in male dogs especially aged male dogs exhibiting visible or palpable enlargement of one or both the pain on palpation of the scrotal area, history of constipation, signs of feminization syndrome like bilateral symmetrical alopecia and others by clinical examination, radiography and ultrasound and by retorting to pathological aids such as cytology and histopathology to confirm the type of testicular tumour (Subapriya et al. 2019) [13] . With the abovementioned information, the manuscript provides a detailed account of the epidemiological, haematobiochemical and cytological characteristics of SCTs in dogs.

Materials and Methods

Clinical samples collected from client-owned dogs presented with complaints of testicular enlargement to the Small Animal Surgery Outpatient Ward and the Small Animal Operation Theatre, Department of Surgery, Madras Veterinary College Teaching Hospital (MVCTH), Chennai-07, for the diagnosis of testicular tumours were the subject of our study. The samples collected included blood, serum, fine-needle aspiration cytology (FNAC) samples, and impression smears from dogs suspected of having testicular tumours. All samples were processed at the Centralized Clinical Laboratory, Madras Veterinary College, Chennai-07. Cytological smears were stained using the Leishman-Giemsa (LG) cocktail stain and examined for neoplastic features as per the criteria described by Subapriya (2019) [14] . For each confirmed case of SCT, details such as breed and age were documented to assess the possible influence of these factors on the development of SCT.

Results and Discussion Incidence

During the study period, Sertoli cell tumours (SCTs) were confirmed by cytological examination in 19 dogs that were clinically and radiographically suspected of having testicular tumours. These confirmed cases accounted for an incidence of 0.34% of all tumours diagnosed in dogs during the study period. Among the nineteen confirmed SCT cases, four dogs exhibited dermatopathological changes in addition to testicular enlargement, as recorded in the sample processing requisition forms. Recognition of such dermatological alterations in dogs presenting with testicular enlargement is clinically significant, as they aid in differentiating SCT from seminoma, both of which may present with similar testicular changes.

Dermatological manifestations such as hyperpigmentation and bilateral symmetrical alopecia around the genital region are more frequently associated with SCT than seminoma, owing to estrogen overproduction and the development of hyperestrogenism syndrome in SCT inflicted dogs. Hence dermatological manifestations of feminization in dogs with testicular enlargement provide an added probability for the testicular tumour to be clinically suspected for SCT which can be further confirmed by pathological screening. Early identification of such characteristic dermatological signs also enables timely initiation of appropriate medical management to counteract the systemic effects of hyperestrogenism in the SCT affected dogs in addition to the surgical intervention of resecting the tumour masses.

Breed

SCTs were identified across six dog breeds in the study, with the highest incidence recorded in Spitz (n=7), German shepherd (n=4), and Dobermann (n=3) breeds, followed by other breeds (Fig. 1). Similar to our findings, Weaver (1983) [15] have also recorded higher occurrence of SCTs in German shepherd breed.

Age

Regarding age wise distribution, the highest number of SCT cases was recorded in adult dogs aged 5-10 years (n = 11), followed by senior dogs over 10 years of age (n = 6), and young adults between 1-5 years (n = 2). The overall age of affected dogs ranged from 3 to 15 years. These findings are consistent with Gazin et al. (2022) [4] , who reported an age range of 2 to15 years and a mean age of 9.4 years for dogs diagnosed with SCT. Among the geriatric cases in the present study, SCTs were recorded in a 15-year-old male Spitz and a 14-year-old male German Shepherd. No cases were identified in dogs younger than one year of age (Fig. 2).

Cytological findings

Cytological evaluation of the SCT cases revealed neoplastic cells arranged both as individually scattered solitary cells and as loosely cohesive cell aggregates. The tumour cells exhibited mild to moderate anisocytosis and anisokaryosis. Nuclei were round to oval with coarse chromatin and contained either prominent single to multiple nucleoli in most of the cases and inconspicuous nucleoli in few cases. The neoplastic cells showed a moderate amount of basophilic cytoplasm, often containing variably sized coarse clear cytoplasmic vacuoles. An altered nuclear-to-cytoplasmic ratio was evident, and mitotic figures were rarely observed. The cytological characteristics of SCT observed in the study were consistent with the descriptions of SCT reported by Sharkey et al. (2010) [10] and Burton (2017) [3] . Representative cytological findings are shown in Fig. 3,4.

Haematobiochemical changes

Serum biochemical analysis of samples from confirmed Sertoli cell tumour (SCT) cases revealed all parameters to be within normal reference range. Haematological evaluation showed that, among the nineteen SCT-positive dogs, anaemia was recorded in five cases, as evidenced by reduced haemoglobin (Hb g/dL), packed cell volume (PCV %), and total erythrocyte count (millions/cmm) in automated haematology analysis, and further supported by microscopic examination of Leishman-Giemsa stained blood smears.

Leukocytosis, characterized by neutrophilia, was observed in two cases, while thrombocytopenia was recorded in three cases. Borbil and Catoi (2007) [2] described the haematological consequences of SCT in dogs stating that due to SCT, severe bone marrow suppression occurs in the affected dogs with resultant increased granulocytopoiesis and neutrophilic leukocytosis for a transient period followed by decreased hematopoiesis leading to progressive leukopenia, thrombocytopenia, and nonregenerative anemia. In this direction, the authors further stated that, subsequent to reduction in blood cells on bone marrow suppression, death may also happen in dogs affected with SCTs due to hemorrhagic episodes occurring due to thrombocytopenia and overwhelming bacterial infection occurring due to leukopenia.

Similarly, Kazarian et al. (2025) [6] also recorded haematological changes such as anemia and leukocytosis in a 13-year-old male dog diagnosed with SCT. The above statements are in support of the haematological findings of anaemia, leukocytosis and thrombocytopenia recorded in dogs cytologically diagnosed with SCTs in our study. SCTs are commonly associated with feminization syndrome and estrogen-mediated systemic effects such as bone marrow suppression and hence assessment of the endocrine profile in tumour affected dogs is advisable. Evaluation of hormonal markers, including oestradiol, estrone sulphate, serum anti-Müllerian hormone (AMH), inhibin-B, and testosterone, can guide appropriate medical management to counteract the adverse effects of hyperestrogenism. Following diagnosis, the prognosis for SCT tend to be favourable when the tumour is unilateral and managed through surgical excision. In contrast, cases involving bilateral testicular involvement or metastatic spread may carry a guarded to poor prognosis.

Acknowledgement

AcknowledgementThe authors are thankful to the Director of Clinics, TANUVAS, Madras Veterinary College Campus, Chennai-07 for the support provided during the study period.

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