Uterine Adenomyosis in Beagle Dogs

211 Uterine Adenomyosis in Beagle Dogs Hak Soo Kim 1, 2 , Sang- Chul Kang 2,3 , Hu-Song Zhang 2 , Jin Seok Kang 4,5 , Jae-Hoon Kim 3 , Kap -Ho Kim 2 , Boo -Hyon Kang 2 and Byung-IL Y oon 1,5, * 1 College of V eterinar y Medicine & Institute of V eterinar y Science, Kangwon National University , Chuncheon , K orea 2 P reclinical R esearch Center , Chemon Inc., Y ongin , K orea 3 College of V eterinar y Medicine, Jeju National University , Jeju, K orea 4 Depar tment of Biomedical Laborator y Science, Namseoul University , Chonan , K orea 5 P eer R eview W orking Group of P reclinical R esearch Center , Chemon Inc., Y ongin , K orea Adenomyosis is a nonneoplastic hyperplastic lesion, characterized by invagination of proliferating endometrial glands into myometrium. In dogs, uterine adenomyosis is relatively rare and it is important in T oxicologic P athology to differentiate other non-neoplastic and neoplastic lesions in uterus. In the present study , we report two cases of adenomyosis in the female beagle dogs used for a chemical toxicity test. Clinically , one out of the two female beagle dogs, 15 months of age, had vaginal bleeding for 2 weeks and the other one, 11 months of age, showed swelling of vulva for a week. At necropsy , the weight of uterus was markedly increased to 27.9 g and 15.8 g, compared with the mean value (4.01 ± 2.37, n=6) of that of other normal dogs, respectively . The parameters of hematology and serum chemistry were ranged normal in both of the dogs with enlarged uterus. F or differentiation of connective tissue with muscle fibers, V an Gieson stain was also performed in the serial tissue sections. Histopathologically , the lesions of the enlarged uteruses were characterized by proliferating endometrial glands into myometrium, surrounded by connective tissue. The endometrial glands were proliferating downward to myometrium or embedded in multiple clustered glands in deeper myometrium without compressing the adjacent muscle fibers. The gland epithelial cells are uniformly cuboidal shape with a dense and bottom-located nucleus. These gross and histological findings were consistent with adenomyosis. K ey words: Adenomyosis, endometrial hyperplasia, beagle, uterus. Received 6 May 2010; Revised version received 14 June 2010; Accepted 15 June 2010 Adenomyosis is a nonneoplastic hyperplastic lesion, characterized by invagination of proliferating endometrial glands into myometrium. Adenomyosis can occur in many species including dogs, cats, rodents and non-human primates (T amada et al. , 2005; Bulman-Fleming , 2008; Hur et al ., 2008; Schlafer and Gifford, 2008; Graham et al. , 2009). This altered change is relatively frequently found in the mouse and less frequently in the rat (Greaves, 1990). In dogs, uterine adenomyosis is relatively rare and usually found as an incidental lesion and it is important in T oxicologic P athology to differentiate other non-neoplastic and neoplastic lesions in uterus (Nielsen and K ennedy , 1990; MacLachlan and K ennedy , 2002). The invasive glands consist of uniform, normal appearing epithelial cells, surrounded by endometrial stroma, within the myometrium (Nielsen and K ennedy , 1990; MacLachlan and K ennedy , 2002; Schlafer and Gifford, 2008). The glands may be small and have the appearance of an endometrial gland, or they may be multiple, or larger with more proliferative endometrial epithelial cell lining (Schlafer and Gifford, 2008). In dogs, an extreme case of uterine adenomyosis may produce “ Swiss cheese ” pattern in the uterine wall (Schlafer and Gifford, 2008). The importance of uterine adenomyosis has not yet been defined in terms of the safety assessment. Adenomyosis is classified as T ype IIE response with cystic endometrial hyperplasia, squamous metaplasia, endometrial polyp and endometriosis, all associated with the estrogenic effects (Haschek and Rousseaux, 1998). However , its underlying mechanism is still unclear . In the presents study , we report two cases of adenomyosis *Corresponding author: Byung -IL Y oon, College of V eterinary Medicine & Institute of V eterinary Science, Kangwon National University , 192-1 Hyoja- dong , Chuncheon, Gangwon 200-701, Republic of K orea T el: +82-33-250-8679 F ax: +82-33-244-2367 E-mail: [email protected] Lab. A nim. Res. 2010: 26(2), 211-213 Case Report 212 Hak Soo Ki m et al. Lab. A nim. Res. | June, 2010 | Vol. 26, No. 2 spontaneously found in the beagle dog which has been commonly used for preclinical safety assessment and discuss its clinical and histopathological characteristics, compared to other non-neoplastic and neoplastic lesions in uterus. Clinically , one out of the two female beagle dogs, 15 months of age, had vaginal bleeding for 2 weeks and the other one, 11 months of age, showed swelling of vulva for a week. At necropsy , the uteri of the dogs were markedly enlarged (F igure 1A); the weight of uterus was increased to 27.9 g and 15.8 g , compared with the mean value (4.01 ± 2.37, n=6) of that of other normal dogs, respectively . The parameters of hematology and serum chemistry were ranged normal in both of the dogs with enlarged uterus (data not shown). The enlarged uterus of each dog was fixed in 10% neutral buffered formalin and, after routine tissue processing , tissues sections were prepared for hematoxylin and eosin stain and examined under light microscope. F or differentiation of connective tissue with muscle fibers, V an Gieson stain was also performed in the serial tissue sections. Briefly , after deparaffinization and hydration, they were stained by W eigert’s hematoxylin and V an Gieson ’s solution for 10 min and 15 min, respectively . Histopathologically , the lesions of the enlarged uteruses were characterized by proliferating endometrial glands into myometrium, surrounded by connective tissue (F igure 1B - 1D). The endometrial glands were proliferating downward to myometrium or embedded in the multiple clustered glands in deeper myometrium without compressing the adjacent muscle fibers (F igure 1C). The gland epithelial cells are uniformly cuboidal shape with a dense and bottom-located nucleus (F igure 1C). These gross and histological findings were consistent with adenomyosis. Despite of some confusion in cases, adenomyosis may usually be differentiated from other non-neoplastic lesions such as endometriosis, cystic endometrial hyperplasia and pseudo -plancentational endometrial hyperplasia and benign uterine tumors such as leiomyoma, in particular adenomyoma. Endometriosis is defined as the presence of endometrial tissue in locations distant to the uterus, usually in the peritoneal cavity (Leininger an d Jokinen, 1990). In ge neral, endometriosis has the tissue resembling endometrium lying outside the endometrial cavity . Cystic endometrial hyperplasia is limited in endometrium and it can be induced by estrogen (T ype IIE response) or more frequently progesterone in the dog (T ype IIP response) (Nielsen and K ennedy , 1990). Cystic endometrial hyperplasia generally arises from endometrial glandular epithelium, but it also develops from villous folds covered by luminal epithelium. Since this condition with exudates accumulation is frequently associated with inflammation and bacterial infection, it may progress to development of pyometra, namely cystic hyperplasia/ Figure 1. Gross and microscopic findings of adenomy osis. The uteri of the dogs w ere markedly enlarged (A). Note the proliferating endometrial glands into my ometrium (M) from endometrium (E, upper of line) (B). Some multiple clustered endometrial glands w ere also found w ith being embedded in deeper my ometrium w ithout compressing the adj acent muscle fibers (C). The glandula r epithelial cells are uniformly cuboidal shape w ithout cellular aty pia. The glands w ere surrounded by connective tissue (deep re d in D). H&E st ain for B and C and V an Gieson st ain for D. Bars=100 µ m for C and D and 200 µ m for B. Uterine adenomy osis in Beagle dogs 213 Lab. A nim. Res. | June, 2010 | Vol. 26, No. 2 pyometra complex (Schlafer and Gifford, 2008). Pseudo - plancentational endometrial hyperplasia is also a kind of endometrial hyperplasia, resembling maternal placental tissues. It has been known to occur primarily during the luteal phase of the cycle when the endometrium is highly sensitive (Schlafer and Gifford, 2008). However , the histological features, as they have the normal histology of the endometrium at placentation sites in normal pregnancy , are very much different from adenomyosis (Schlafer and Gifford, 2008). Another confusing lesion in uterus with adenomyosis is leiomyoma. But unlike leiomyoma, adenomyosis has indistinct, poorly delimited margins from the adjacent myometrium (Bergeron et al ., 2006). In the present study , foci of adenomyosis were surrounded by connective tissue and normal smooth muscle cells without compression. In human, adenomyoma which appear to be histologically very similar with adenomyosis is characterized by a circumscribed, nodular aggregate of smooth muscle, endometrial glands and stroma (Bergeron et al ., 2006). However , in the domestic and experimental animals, adenomyoma has not been documented in the literature. In terms of differential diagnosis based on the clinical symptoms, it is difficult to differentiate those uterine lesions described above. In this study , one dog had bleeding for 2 weeks, although we were not sure if it is due to adenomyosis or not. The cause(s) and mechanisms of adenomyosis are unclear , but it is most likely to originate from the deep part of the endometrial mucosa (Bergeron et al ., 2006). The lesions supporting this hypothesis were also noted in the present study; the endometrial glands located in the deep part of endometrium invaded into myometrium with surrounding stroma. Indeed, it was found that estradiol receptor expression is greater in the adenomyotic foci than in the normal endometrium with an association with apoptosis -regulating bcl-2 gene product which reaches peak during the proliferative phase of the menstrual cycle (Otsuki et al ., 1994). Adenomyosis frequently occurs with other estrogenic effects such as cystic endometrial hyperplasia, squamous metaplasia, endometrial polyp and endometriosis, suggesting that it is associated hyper - estrogenic states (Greaves, 1990). Another hypothesis is that adenomyosis may originate and develop through metaplasia from de novo ectopic intramyometrial endometrial tissue which is capable of differentiating both glands and stroma (Bergeron et al. , 2006). In summary , in the present study , we first reported two cases of adenomyosis in the beagle dogs used for a preclinical toxicity study in K orea. 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