Rete Ovarii Research Articles

Rediscovering the Rete Ovarii: a secreting auxiliary structure to the ovary.

The rete ovarii (RO) is an appendage of the ovary that has been given little attention. Although the RO appears in drawings of the ovary in early versions of Grays Anatomy, it disappeared from recent textbooks, and is often dismissed as a functionless vestige in the adult ovary. Using PAX8 immunostaining and confocal microscopy, we characterized the fetal development of the RO in the context of the ovary. The RO consists of three distinct regions that persist in adult life, the intraovarian rete (IOR), the extraovarian rete (EOR), and the connecting rete (CR). While the cells of the IOR appear to form solid cords within the ovary, the EOR rapidly develops into a convoluted tubular epithelium ending in a distal dilated tip. Cells of the EOR are ciliated and exhibit cellular trafficking capabilities. The CR, connecting the EOR to the IOR, gradually acquires tubular epithelial characteristics by birth. Using microinjections into the distal dilated tip of the EOR, we found that luminal contents flow towards the ovary. Mass spectrometry revealed that the EOR lumen contains secreted proteins potentially important for ovarian function. We show that the cells of the EOR are closely associated with vasculature and macrophages, and are contacted by neuronal projections, consistent with a role as a sensory appendage of the ovary. The direct proximity of the RO to the ovary and its integration with the extraovarian landscape suggest that it plays an important role in ovary development and homeostasis.

Bulk and single-cell transcriptome datasets of the mouse fetal and adult rete ovarii and surrounding tissues

The rete ovarii (RO) is an epithelial structure that arises during development in close proximity to the ovary and persists throughout adulthood. However, the functional significance of the RO remains elusive, and it is absent from recent discussions of female reproductive anatomy. The RO comprises three regions: the intraovarian rete within the ovary, the extraovarian rete in the periovarian tissue, and the connecting rete linking the two. We hypothesize that the RO plays a pivotal role in ovarian homeostasis and responses to physiological changes. To begin to uncover the nature and function of RO cells, we conducted transcriptomic profiling of the RO. This study presents three datasets, and reports our analysis and quality control approaches for bulk, single-cell, and nucleus-level transcriptomics of the fetal and adult RO tissues using the Pax8-rtTA; Tre-H2B-GFP mouse line, where all RO regions express nuclear GFP. The integration and rigorous validation of these datasets will advance our understanding of the RO’s roles in ovarian development, female maturation, and adult female fertility.

Cystadenoma in the <em>rete ovarii</em> in a bitch

The rete ovarii is the counterpart of the male rete testis that develops from the primary sex cords of female animals. Pathological conditions of the rete ovarii are rarely reported in dogs. This communication describes a cystadenofibroma of a rete ovarii in a 2-year-old, intact, crossbred bitch presented to the Veterinary Teaching Hospital, University of Peradeniya. The bitch was presented with complaints of hyporexia, constipation, purulent vaginal discharges and progressive abdominal distension for three weeks. A tentative diagnosis of pyometra with concurrent uterine cyst/neoplasia was arrived based on the clinical examination and imaging findings. An exploratory laparotomy revealed that the space of the right ovary is occupied by a large, 14 cm x 16 cm, smooth surfaced, spherical mass and ovariohysterectomy was performed. Histopathology findings of the cyst suggested a cystadenofibroma of rete ovarii. To the authors’ knowledge, this is the first report of canine cystadenofibroma in rete ovarii in Sri Lanka.

Integration of mouse ovary morphogenesis with developmental dynamics of the oviduct, ovarian ligaments, and rete ovarii.

Morphogenetic events during the development of the fetal ovary are crucial to the establishment of female fertility. However, the effects of structural rearrangements of the ovary and surrounding reproductive tissues on ovary morphogenesis remain largely uncharacterized. Using tissue clearing and lightsheet microscopy, we found that ovary folding correlated with regionalization into cortex and medulla. Relocation of the oviduct to the ventral aspect of the ovary led to ovary encapsulation, and mutual attachment of the ovary and oviduct to the cranial suspensory ligament likely triggered ovary folding. During this process, the rete ovarii (RO) elaborated into a convoluted tubular structure extending from the ovary into the ovarian capsule. Using genetic mouse models in which the oviduct and RO are perturbed, we found the oviduct is required for ovary encapsulation. This study reveals novel relationships among the ovary and surrounding tissues and paves the way for functional investigation of the relationship between architecture and differentiation of the mammalian ovary.

OP-3 - Immunohistochemical analyses of steroid hormone receptors in the Wolffian remnants of female mice

The developing mesonephros contains the mesonephric duct, mesonephric tubules, and rete cells. In males, they differentiate into the epididymal duct, efferent tubules, and rete testis, respectively. These structures in females cease development and persist as the epoöphoron and rete ovarii. The morphology and function of the female reproductive organs are closely related to steroid hormones. Therefore, we examined the expression of steroid hormone receptors in the epoöphoron and rete ovarii to clarify whether these remnants can react to the steroid hormones in adult female mice. Serial paraffin sections of ovaries collected from adult C57BL/6 J mice were prepared. Androgen receptor (AR), estrogen receptor (ESR1), progesterone receptor (PR), Ad4BP as a marker for the rete ovarii, and Pax2 as a marker for the epoöphoron were detected by immunohistochemistry. Additionally, the rete ovarii and epoöphoron were reconstructed in Amira software from image data of the serial sections. The rete ovarii was positive for Ad4BP at the hilum of ovary, and Pax2 was detected in the epoöphoron within the adipose tissue around the ovary. Pax2 was also found in a part of epithelial cells of the rete ovarii. The Pax2 positive epithelial cells of the epoöphoron and rete ovarii were also positive for AR and ESR1. The PR expression was confirmed in neither the rete ovarii nor epoöphoron. Three-dimensional reconstruction confirmed a convoluting duct, which divided 3-4 branches extending toward the rete ovarii. The Pax2-positive epithelium of the rete ovarii also protruded to the epoöphoron. However, no contact between the rete ovarii and epoöphoron was found in almost all cases. The epithelium of mesonephric tubules, which have connected to the rete ovarii, is suggested to be partially stranded on the rete ovarii during the regression in the female mouse. These epithelial cells left in the postnatal rete ovarii probably retain the sensitivity for androgen and estrogen.

Origin, specification and differentiation of a rare supporting-like lineage in the developing mouse gonad.

Gonadal sex determination represents a unique model for studying cell fate decisions. However, a complete understanding of the different cell lineages forming the developing testis and ovary remains elusive. Here, we investigated the origin, specification, and subsequent sex-specific differentiation of a previously uncharacterized population of supporting-like cells (SLCs) in the developing mouse gonads. The SLC lineage is closely related to the coelomic epithelium and specified as early as E10.5, making it the first somatic lineage to be specified in the bipotential gonad. SLC progenitors are localized within the genital ridge at the interface with the mesonephros and initially coexpress Wnt4 and Sox9. SLCs become sexually dimorphic around E12.5, progressively acquire a more Sertoli- or pregranulosa-like identity and contribute to the formation of the rete testis and rete ovarii. Last, we found that WNT4 is a crucial regulator of the SLC lineage and is required for normal development of the rete testis.

Electrolyte, Oestradiol and Progesterone Concentrations in Ovarian Cyst Fluid in Guinea Pigs (Cavia porcellus)

Despite their high prevalence, the aetiopathogenesis of ovarian cysts in guinea pigs (Cavia porcellus) is unknown. We examined tissue samples of cystic ovaries from 20 guinea pigs by histopathology and immunohistochemistry for CD10 antigen, and determined the concentrations of Na+, K+, Cl-, oestradiol and progesterone in the cyst fluid. Cystic rete ovarii were found in all 20 guinea pigs but no follicular cysts. Concentrations of Na+ (142.2±5.04mmol/l), K+ (5.6±0.76mmol/l) and Cl- (116.1±5.25mmol/l) corresponded to extracellular, rather than intracellular, fluid indicating that rete ovarii cysts in guinea pigs are transudative in nature. A positive correlation was found between Na+ and Cl- concentrations (r=0.7713, P<0.0001). The mean concentrations of oestradiol (61.9±17.44pg/ml) and progesterone (2.7±5.42ng/ml) in the cyst fluid were higher than expected because the rete epithelium is not known to have steroidogenic activity. A negative correlation was found between oestradiol and progesterone concentrations in cyst fluid (r=-0.4296, P=0.0178). Possible pathogenetic mechanisms of cystic rete ovarii in guinea pigs are discussed.

Squamous metaplasia of the rete ovarii do not suppress ovarian cyclicity and pregnancy in cattle: case report

ABSTRACT Squamous metaplasia of the rete ovarii is an ovarian pathologic change characterized by replacement of the normal single layered cuboidal epithelium of the rete ovarii by a stratified squamous keratinized epithelium. Uterus and ovaries from a local slaughterhouse pregnant crossbreed cow were evaluated through ultrasound, macroscopically and histologically. Grossly, there were multiple cysts in both ovaries, which were histologically characterized as rete ovarii cysts with squamous metaplasia and intraluminal accumulation of keratinized material. Squamous metaplasia of the rete ovarii has been previously reported in cows, however this is the first report of this condition in a pregnant animal, demonstrating that this ovarian change is compatible with pregnancy.

The morphological and histological study of chicken left ovary during growth and development among Hy-line brown layers of different ages

Chicken ovaries are known to develop asymmetrically and only the left ovary fully develops. Although both have been greatly investigated, a gap in scientific reports is still felt between 2-mo-old and sexual maturity. In this study, we aimed at investigating the changes in components that occur during growth to analyze the morphohistological correlation between the left ovary and the follicle development at different age stages in Gallus domesticus. The ovaries were harvested from 60 chickens aged 1 and 3-wk-old, 1, 2, 3, and 4-mo-old (n = 10 per age group), then fixed in AAF solution. Hematoxylin-and Eosin protocol was used to stain the tissue for microscopic observations. Results revealed that the left ovary exhibited an ovarian tissue, a site of follicular growth that displayed various shapes from smooth to greatly indented as the follicles differentiated. Atretic follicles at various regression stages were noticed frequently as the chicks grew in age from 3-wk-old onward along with their differentiation. Rete ovarii, remnants from the male homologs were observed throughout the whole study showing epoöphoron, connecting rete, and gland-like structures that tend to diminish with age. The feature of the left ovary is closely related to the follicular developmental stage, and the bigger and differentiated the follicles are, the more indented and irregular its epithelium appears. Atresia is a normal physiological process that we observed throughout the whole study. Also that, rete ovarii do not spontaneously arise in the ovary but it develops and grows in juvenile chicken as well as in adult ones.

Mast cells and Kurloff cells - Their detection throughout the oestrous cycle in normal guinea pig ovaries and in guinea pigs with cystic rete ovarii

Mast cells (MCs) and Kurloff cells (KCs) were detected in guinea pig ovaries in the follicular and luteal phases of the oestrous cycle. The samples of ovaries were fixed in Mota's basic lead acetate. Toluidine blue was used for detection of MCs and periodic acid-Schiff for detection of KCs. The percentage of KCs in a differential leukocyte count was determined in blood smears stained according to the Pappenheim method. Non-pregnant females with normal ovaries and with cystic rete ovarii were included in the study and the numbers of MCs and KCs were compared in these two groups and in follicular and luteal phases of the oestrous cycle. MCs' distribution in ovaries was different in the guinea pig in comparison to previously studied species: MCs were found exclusively in the superficial layers of cortical stroma and no significant difference was found between the number of MCs in the follicular and luteal phases, neither in normal ovaries, nor in ovaries with cystic rete ovarii. Significantly lower numbers of MCs were found in ovaries with cystic rete ovarii (P < 0.01) in contrast to normal ovaries. A significantly higher percentage of KCs in the peripheral blood was found in the follicular phase (P < 0.05), whereas no significant difference was found in relation to the presence of cystic rete ovarii. Interestingly, no KCs were found in the samples of ovaries (either in the follicular or luteal phase, and with or without cysts). Thus, the expected role of KCs in ovarian physiology or in the aetiology of the cystic rete ovarii can be excluded.

Brenner tumor associated with rete ovarii: a histologic and immunohistochemical analysis of six cases exploring the relationship between these entities

The association of Brenner tumor (BT) with rete ovarii (RO) has been rarely alluded to in the literature. Both entities have debatable histogenesis. In this study of six cases of BT associated with RO, we describe the morphologic features and performed immunohistochemical staining for markers of Mullerian, Wolffian, mesothelial, and sex cord stromal derivation to explore the relationship between these entities. Histologically, all BTs were benign, microscopic, and incidental. RO was prominent and hyperplastic with gradual or abrupt transition to BT. In addition, focal areas of rete entrapped between BT nests were seen. All BTs were positive for GATA-3 and negative for PAX-8. Conversely, the RO in all cases was negative for GATA-3 and positive for PAX-8. WT-1 was positive in both entities. Sex cord stromal and mesothelial markers (other than WT-1) were negative in BT and RO. Although morphologically, BTs seem to arise from RO in these cases, they have a distinct immunophenotype. It is possible that at least some BTs arise from metaplastic changes in RO epithelium.

The immunoexpression patterns of fibroblast growth factors in the pregnant and postpartum rat ovary.

Fibroblast growth factors (FGFs) are polypeptides involved in the regulation of oogenesis and folliculogenesis by inducing ovarian mitogenic, homeostatic and angiogenic activity. This study was aimed at determining the localisation of FGF ligands (FGF1 and FGF2) and FGF receptor 2 (FGFR2) in the rat ovary by immunohistochemical analyses, at pregnancy and the postpartum period. During pregnancy and the postpartum period, positive FGF1 immunoreactions were observed in the nucleus and cytoplasm of germinative epithelial cells, granulosa cells of follicles in different developmental stages, theca interna cells, interstitial cells, luteal cells and atretic follicles. FGF2 immunoreactivity was strong in the cytoplasm of the endothelial cells and smooth muscle cells of the ovarian blood vessels and in the smooth muscle cells of the ovarian cortex and medulla. Strong FGFR2 immunoreactivity was observed in the stromal cells surrounding the blood vessels and rete ovarii. Immunoreaction intensity of the FGF1, FGF2 and FGFR2 had relatively similar abundances between the periods examined. Considering that FGFs act as local regulators in oogenesis, folliculogenesis, follicular atresia, ovulation, corpus luteum formation and regression and angiogenesis, this study supports the idea that FGFs may also be involved in these physiological functions in rat ovaries during pregnancy and postpartum period.

Histopathological findings in the uteri and ovaries of clinically healthy cats presented for routine spaying.

The aim of this study was to assess the histopathological findings in the uteri and ovaries from clinically healthy queens presented for elective spaying. Ovaries and distal uterine horns or complete uteri from 106 female cats were evaluated for pathological alterations. Pathological alterations of the uterus and/or ovaries were evident in 29 cats; of these, corpora lutea were present on the ovaries of 15 cats. Ovarian cysts were found in 15 cats and were classified as cysts of the Wolffian or Muellerian ducts (n = 4), follicular cysts (n = 4), luteal cysts (n = 1), cystic rete ovarii (n = 2), combinations of different cysts (n = 2) and non-classifiable cysts (n = 2). In 21/106 cats, cystic endometrial hyperplasia (CEH) was present. The incidence of CEH increased with the age of the cat. Six cats had purulent endometritis with or without distension of the uterine lumen. Hyperplastic lesions of the endometrium were detected in two cats. In one cat, a uterine horn malformation with duplication of one uterine horn lumen was diagnosed. Whereas the majority of ovarian cysts and slight-to-moderate CEH are unlikely to interfere with an animal's wellbeing, endometritis must be considered a serious health problem that requires veterinary attention.

Formation of the rete testis during mouse embryonic development.

The rete testis connects seminiferous tubules of the testis with efferent ducts having a mesonephric origin. The development of the rete testis is insufficiently studied, but there is evidence suggesting that it originates from gonadal cells. Here, the formation of the rete testis was investigated from E11.5 to E16.5 using immunofluorescent staining and 3D-modeling. The rete testis became visible by SOX9 and PAX8 staining starting from E12.5. It was located in the mesonephros but connected with testis cords formed by Sertoli cells expressing SOX9, AMH, DMRT1. Between E13.5 and E14.5, AMH+ network of testis cords at the mesonephric side began to disintegrate in a gradient-dependent manner along the anterior-posterior axis of the gonad and connections between testis cords gradually lost AMH becoming a part of the rete. Cells combining features of Sertoli and rete cells (PAX8+ AMH+ and DMRT1+ AMH- cells) were detected starting from E14.5, suggesting that some rete cells originated from Sertoli cells. The rete ovarii, a female counterpart of the rete testis, developed in a similar way as the rete testis until E13.5. A part of the rete testis originates from connections between testis cords. Evidence that Sertoli cells contribute to rete cells is provided.

The ovarian stroma as a new frontier.

Historically, research in ovarian biology has focused on folliculogenesis, but recently the ovarian stroma has become an exciting new frontier for research, holding critical keys to understanding complex ovarian dynamics. Ovarian follicles, which are the functional units of the ovary, comprise the ovarian parenchyma, while the ovarian stroma thus refers to the inverse or the components of the ovary that are not ovarian follicles. The ovarian stroma includes more general components such as immune cells, blood vessels, nerves, and lymphatic vessels, as well as ovary-specific components including ovarian surface epithelium, tunica albuginea, intraovarian rete ovarii, hilar cells, stem cells, and a majority of incompletely characterized stromal cells including the fibroblast-like, spindle-shaped, and interstitial cells. The stroma also includes ovarian extracellular matrix components. This review combines foundational and emerging scholarship regarding the structures and roles of the different components of the ovarian stroma in normal physiology. This is followed by a discussion of key areas for further research regarding the ovarian stroma, including elucidating theca cell origins, understanding stromal cell hormone production and responsiveness, investigating pathological conditions such as polycystic ovary syndrome (PCOS), developing artificial ovary technology, and using technological advances to further delineate the multiple stromal cell types.

Ovarian neoplastic changes in dairy cows with adenomyosis - histopathological study

IntroductionThis paper presents the results of the microscopic examination of dairy cow ovaries.Material and MethodsThe examined dairy cows were culled in a slaughterhouse. In all of them, pathological changes (n = 82) associated with adenomyosis had been previously diagnosed, and additionally in some cows (n = 18) so had mammary gland cell injury, including mastitis purulenta.ResultsThere was vast variability among the investigated individuals in the degree of disease and type of pathological changes in the examined tissue specimens. In all examined ovaries, the most prominent lesions were neoplastic metaplasia of various cell types. They were PEComa, rete ovarii cell neoplasm, granulosa cell tumour, and a single case of haemangioma cavernosum, and the first of these types of ovarian tumours was the prominent neoplasia. In some cases, they grew simultaneously with the other types of tumours, but tumour tissue never extended beyond the ovarian capsule. Sometimes, the ovarian tumours were of microscopic volume, for instance the foci of granulosa cell tumours.ConclusionThe lack of changes in ovarian anatomic structure, and minute neoplastic tissue foci, make it impossible to diagnose these lesions in the ovaries of living animals. The presented original data may be valuable in understanding the aetiology of dairy cow infertility, as well as in facilitating urgently needed research into findings new methods, which might be used in the diagnosis of neoplastic diseases ante mortem.

Development of the sheep ovary during fetal and early neonatal life and the effect of fecundity genes

In female sheep fetuses, the mesonephros and genital ridge can be identified at days 20 and 23 of gestation (term = 145 days), respectively. Moreover oogonia can be observed at the genital ridge from as early as day 23. Around day 55 of gestation, some germ cells enter meiosis coincident with the arrival of mesonephric-derived somatic cells (i.e. the rete ovarii). From days 75, 100, 120 and 135 of gestation, primordial (one layer of flattened granulosa cells), primary (one complete layer of cuboidal granulosa cells; early preantral), secondary (preantral) and tertiary (antral) follicles, respectively, develop within the innermost regions of the ovarian cortex. During the early neonatal period highly variable numbers of antral follicles may be present. After examination of Booroola fetuses from day 28 of gestation, it seems that the FecBB gene is associated with retarded development of the heart (day 28) mesonephros (days 30–40) and from day 30 to early neonatal life, the ovary. With respect to the ovary, fewer oogonia (days 30–40), primordial follicles (day 75–90) and growing follicles (day 120 to 6 weeks after birth) have been observed in females carrying the FecB gene. By contrast, the FecB gene is not associated with differences in plasma gonadotrophin or immunoreactive inhibin until early neonatal life. In Inverdale (I) fetuses heterozygous for the FecXI gene (I+), retarded germ cell development was observed at days 40 and 90 of gestation. In putative homozygous carriers (II) of the Inverdale gene, germ cell development appeared normal until day 100, but thereafter from day 120 normal secondary follicles were not observed, although many abnormal follicular-like structures were present. In both I+ and II fetuses no obvious differences in gonadotrophin concentrations have been noted. Collectively, the evidence suggests that the fecundity genes FecBB and FecXI, which affect ovulation rate in sexually mature females, are regulating organ differentiation or germ cell maturation or both processes during fetal life.

Genital Tract Pathology in Female Pet Guinea Pigs (Cavia porcellus): a Retrospective Study of 655 Post-mortem and 64 Biopsy Cases

Disorders of the female genital tract are among the most common disorders in pet guinea pigs (Cavia porcellus); however, knowledge of many aspects of these disorders is sparse, especially regarding their incidence and age distribution. Ovarian cysts, as the most common genital tract disorder in guinea pigs, have been investigated in detail; however, information on the nature of these cysts is inconsistent. The present study reviewed genital tract disorders occurring within 655 full post-mortem examinations of intact female pet guinea pigs and 64 female genital tract biopsies examined over a 22.5 year period. Age distribution was determined from 550 post-mortem examinations of animals of known age. Genital tract disorders were found in 295 post-mortem examinations (45.0%) in animals with a median age of 52 months. Additionally, disorders were found in all genital tract biopsy samples from guinea pigs with a median age of 48 months. The incidence of genital tract diseases increased from 1.5% in guinea pigs ≤6 months of age to up to 77.8% in animals >6 years of age. Ovarian cysts were the most common genital tract disorder, found in 245 of the 655 post-mortem cases (37.4%) and 38 of 43 ovarian biopsy samples (88.4%). The incidence of ovarian cysts increased with advancing age, reaching 75.6% in animals >6 years. In 119 cases, histopathology and immunohistochemistry confirmed cystic rete ovarii as the only cyst type. A Fallopian tube adenoma was found in a single case, so disorders of the Fallopian tube should be considered rare. Uterine disorders were diagnosed in 17.4% of the post-mortem examinations and 98.1% of uterine biopsy samples. Uterine neoplasia, hyperplasia and inflammation were common, but occurred at different ages. The incidence of uterine neoplasia and hyperplasia was higher in older animals (>15% in guinea pigs >6 years), while the incidence of uterine inflammation was the highest (17.9%) in animals aged 7-12 months. An association between ovarian cysts and uterine neoplasia or hyperplasia was not evident. Vaginal disorders were rare and included leiomyoma, polyps and vaginitis.

Proceedings of the 2018 National Toxicology Program Satellite Symposium

The 2018 annual National Toxicology Program Satellite Symposium, entitled "Pathology Potpourri," was held in Indianapolis, Indiana, at the Society of Toxicologic Pathology's 37th annual meeting. The goal of this symposium was to present and discuss challenging diagnostic pathology and/or nomenclature issues. This article presents summaries of the speakers' talks along with select images that were used by the audience for voting and discussion. Various lesions and other topics covered during the symposium included seminiferous tubule dysgenesis in rats, ameloblast and odontoblast degeneration/necrosis in a Sprague Dawley rat, intestinal leiomyositis in a beagle dog, gallbladder mucinous hyperplasia, focus of hepatocellular alteration and bile duct alteration in otters, renal tubule cytoplasmic vacuolation with basophilic granules in mice treated swith antisense oligonucleotide therapy, a uterine choriocarcinoma in a rhesus macaque, and rete ovarii proliferative ovarian lesions in various aged rat strains. One particularly provocative lesion was a malignant neoplastic proliferation in the renal pelvic region of a cynomolgus macaque from a 21-day study. Additional challenging lesions included thyroid proliferative lesions in zebra fish and gross findings in fish larvae during routine chemical screening. The Rabbit and Minipig International Harmonization of Nomenclature and Diagnostic Criteria Organ Working Groups also presented a series of challenging lesions.

Effects of Ovarian Pathologies and Uterine Inflammations on Adenomyosis in Bitches

Background: Adenomyosis is a non-neoplastic condition, characterized by the presence of endometrial glands or cells in the myometrium. Adenomyosis is defined by post-operative microscopic examination of uterine tissue and a rarely seen infertility problem in bitches. The process of transformation of healthy uterus into adenomiotic uterus is still a mystery. We aimed to determine role of ovarian pathologies and uterine inflammations on pathogenesis of uterine adenomyosis in bitches.Cases: After ovariohysterectomy, the uteri were fixed and processed by routine methods. Sections were stained with HematoxylinEosin, Masson’s trichrome and Periodic-Acid-Schiff and immunohistochemically; with p53 protein, Ki-67, α-smooth-muscle actin, cytokeratin-CK 8, 14, 19 antibodies, estrogen and progesterone receptors by Avidin-Biotin-Complex-Peroxidase method. Histopathologically, 7 of the collected tissue samples (n = 38) were diagnosed as adenomyosis. There were unilateral (n = 6) or bilateral (n = 1) adenomyosis in which endometrial glands had broken through the myometrium, and in some cases there were fibromyoma, inflammation, papillary hyperplasia and cysts in glands. Vaginal fibroma, fibromyoma and benign mix tumor (n = 1), simple carcinoma (n = 3), carcinosarcoma (n = 3) in mammary gland were determinated histopathologically. In addition to these findings, follicular cysts (n = 4), parovarian cyst (n = 1), adenocarcinoma and Rete ovarii adenoma were diagnosed in some ovaries. The CK 19 was scored at endometrial glands (n = 2) positively and also, muscle fibers were stained positively with α-smooth-muscle actin antibody (n = 7).Discussion: Adenomyosis is an infertility problem in adult dogs and is hard to detect with routine gynecological examinations. Adenomyosis can be seen unaccompanied by other gynecological problems such as endometritis or leiomyomas, while mammary tumors with adenomyosis have been previously reported in women and in only one case of a bitch. Little is known of the interrelationships between gross pathological and endocrine features of ovarian cysts in bitches. Due to the local hormonal imbalance, most of these ovarian tumors and cystic structures might be accompanied with uterine-vaginal and mammary gland pathologies, cystic endometrial hyperplasia-pyometra, adenomyosis, vaginal fibroma and mammary tumors. The hyperestrogenic metabolic state may promote both the invagination process and the overall spreading of adenomyosis into the myometrium. Adenomyosis is often associated with polyps, anovulation, hyperplasia without cytological atypia, and uterine leiomyoma which are produced by hyperestrogenic states. Prolactin appears to induce adenomyosis in mice and hyperprolactinemia may cause myometrial degeneration/weakness and subsequent endometrial invasion in the presence of ovarian steroids in women. Premature decline in progesterone, a problem ensues with prolactin release which can promote hyperprolactinemia or endogenous prolactin release. In addition to hormonal problems, uterine infections, immune factors and their products like cytokines and inflammatory mediators, oxidative stress and free radical metabolism also might have roles in the occurrence of adenomyosis. In the present study, four of seven adenomyotic uterine tissues had inflammation and 3 of 7 cases had pre-inflammatory changes. Changes in uterine tissues may increase cell infiltration and proliferation as well as the activity of immune cells which may promote development of adenomyosis in bitches. It is therefore possible that a defect in the p53 tumor suppressor gene may play an important role in the de novo neoplastic transformation of adenomyosis. In conclusion, adenomyosis can be observed bilaterally or unilaterally in dogs. Tissue damage under the influence of inflammation or hormonal disturbances might have a role in the occurrence of uterine adenomyosis.