Retrospective Study of Tumors at the Genital Tract of Dogs Presented at the Veterinary Hospital of Unisa During the Period of February 2000 to December 2008
G.A.L. Veiga; A. Barbosa; K.S. D'Oliveira; C. Brito; F. Kitahara; J.F. Frignani; M.A.B. Iannone; F.P. Pereira; C.P. Carramenha
The tumors of the genital tract are uncommon in dogs, excepting the testicular tumors and the transmissible venereal tumor (TVT) (McEntee et al., 2002). The actual incidence of these tumors cannot be evaluated as a result of the accomplishment of precocious ovariohysterectomy, absence of histopathologic exams and for being, in some cases, autopsy found (Klein, 2007). The adult animals, over 5 years old, are the most affected and the majority of tumors at the reproductive tract does not present racial predilection. With regards to the females, the main histological types found are leiomyoma, leiomyosarcoma and adenocarcinoma that occur in the uterus and mainly in the vagina. Regarding the males, the sertolinoma and testicular seminoma, preputial mast cell tumor and the prostate carcinoma are the tumors with the most incidences (Hedlund, 2008). The clinical signals vary in accordance with the localization of the tumor, but generally are characterized by the elimination of sanguineous purulent secretion through the external genitalia, alterations of the estral cycle and changes on the sexual behavior as well as, unspecific signals as enlarged abdominal volume, tenesmus, dysuria, hematuria and dermatologic alterations. For the benign tumors, the treatment through the surgical resection is effective and when associate to the sterilization of the animal can prevent the recurrence of the illness, since the majority of the reproductive tumors present influence of hormonal character. The present study has as objective to determine the localization, the most frequent histological types as well as, the epidemiologist profile of the dogs with genital tract tumor seen at the Veterinary Hospital of University of Santo Amaro (Unisa).
Materials and Methods
The total of 256 animals presenting reproductive system tumor was seen in the period of January 2000 to December 2008. The localization of the tumor, the epidemiologic profile (sex, age, breed) as well as the histological types of the tumors were revised. For the accomplishment of the surgical procedure, all the animals were submitted to the physical exam, complementary exams as blood cell count and biochemistry, besides radiographic and ultrasonographic exams, when necessary. The surgical procedures were realized under inhalatory anesthesia, and the fragments of tumor tissue or tumor mass were conserved in formaldehyde solution at 10% for histopathologic exam, when authorized by the proprietor of the animal. The cytological exam was realized only in animals with TVT suspicion. The statistics analysis relative to sex, age, breed and localization of the tumor was based on the total number of seen animals; the incidence of the histological types, for each organ, was analyzed from the total of animals in which the histopathological exam was realized.
Among 256 animals seen with genital tract tumor, the female ones (57.07%) presented the most prevalence in relation to the male ones (42.93%). The dogs over five years old (74%) were most affected (Graph 2) and, the mongrel dogs (59.8%) the most prevalent followed by the Poodles (7%) and the German Shepherd (4.7%) (Graph 3). In relation to the localization, the vaginal tumors presented high incidence (50.78%), followed by the testicular tumors (20.47%). Of the total of seen animals (n = 256), the cytological exam was used only on the animals with TVT suspicion (n = 112), on the remaining (n = 144) was indicated the accomplishment of histopathological exam, however this procedure was authorized in only 56 animals. The following results are referring to the animals in which the diagnosis was confirmed by the cytological exam (TVT) or by the histopathologic exam (n = 168). On the masculine reproductive tract, the most histological types found were the testicular sertolinoma (45.5%), scrotal mast cell tumor (75%), penile TVT (90%) and preputial (75%). Only 2 cases of prostate tumor were submitted to the histopathologic exam, being diagnosed adenocarcinoma and leiomyosarcoma. On the females, the histological types of most incidence were the vaginal TVT (84.60%) and uterine leiomyoma (50%). The ovarian tumors (2.36%) were represented by 2 histological types, being them the teratoma (67%) and the granulosa cell tumor (33%).
Discussion and Conclusions
Retrospective studies in oncology are important to identify some characteristics of the tumors as well as, its biological behavior and factors that can potentially affect the response to several treatments, becoming a therapeutic challenge. The present study reports a variety of information related with sexual, racial and old age predisposition of dogs with genital tumor, associated with the histological type and the localization of these tumors, being these information similar to the other authors. The genital tract is a complex system, composed by different organs with capacity to originate diverse types of tumors, for this reason the reproductive system of dogs presents different incidences in accordance with the place of origin of the tumor. Previous studies demonstrate that testicular tumors as the sertolinoma, seminoma and leidygoma are extremely common, as well as scrotal mast cell tumor (Stone, 1985). These data are confirm the results gotten from this study that reports the high incidence of sertolinoma (45.5%), followed by seminoma (31.8%) and leidygoma (22.7%), in the same way as scrotal mast cell tumor presented superior prevalence (75%) compared to the other histological types. TVT is a common tumor of the external genitalia of young animals, stray and sexually active (Veraschin et al., 2001). The high incidence of TVT on the external genitalia of males (90% of penile tumors and 75% of preputial tumors) and females (84.6% of the tumors of vulva/vagina) can be justified by the high number of stray animals seen at our institution. The low incidence of prostate tumors in our study compared to the incidence of tumors in other organs of the masculine reproductive tract corroborates with the reports from other authors who demonstrate that these tumors are rare in dogs and represent 5% of the prostate affections, being the adenocarcinoma the histological type of most frequency (Stone, 1985; Barsanti & Finco, 1992; Johnston et al., 2001). Uterine tumors are considered rare in female dogs, representing only 0.4% of all tumors in dogs and 1 to 19% of all the female genital tract tumors. Leiomyoma is the most frequent histological type followed by fibroma (Johnston et al., 2001). The malignant uterine tumors are considered extremely rare, and the described histological types include hemangiosarcoma, carcinoma and plasmacytoma (Murakami et al. 2001; Payne-Johnson et al. 1986; Cave et al. 2002; Choi et al. 2004). Our results demonstrate low incidence of uterine tumors (3.93%), with predominance of leiomyoma (50%), however in our study we can report the occurrence of uterine leiomyosarcoma, also considered extremely rare. According to Klein (2007), the germinative cells ovarian tumors as teratoma are rare and represents from 6 to 20% of the cases, whereas the stromal cells tumors, as the granulosa cell tumor, are more incident representing 35% to 50% of the cases. Our results diverge from the previous author, once that teratoma (67%) were more prevalent compared to the granulosa cell tumor (34%). In a general way, the main breeds that present genital tract tumor are the German Shepard, Poodle, Boxer and Yorkshire (Tacher et al., 1983; McEntee, 2002; Klein, 2007). In our study, the related breeds presented significant prevalence, however not surpassed the high incidence of mongrel animals (59.8%), fact that can be justified by the predominance of mongrel dogs on the population seen at the hospital. Making a comparative analysis between males and females relating to the more affected reproductive organ, it was noticed that the incidence of vulvo-vaginal tumors (50.78%) is extremely superior that other organs. In the same way, the number of females (57.07%) presenting genital tract tumor in our study surpasses the number of affected males (42.93%). These results corroborate with previous reports that also demonstrate the high incidence of females presenting genital tumors, being the vagina the place of most frequency, mainly with regard to TVT (Souza et al., 2000; Silva et al., 2007). It can be concluded that amongst the tumor processes of the genital system, the formations in external genitalia were the most prevalent in the evaluated cases, being the TVT the most frequently diagnosed, probably due to the great number of dogs with free access to the street on the population seen at this hospital.
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