An epidemiologic study of canine multiple primary neoplasma involving the female and male reproductive systems

The significance of canine multiple primary neoplasms involving the reproductive system and one or more additional anatomic sites was evaluated using data from the Alameda and Contra Costa County Animal Tumor Registry. Among the registry's data base of 35 015 histologically confirmed tumors, both sequential and simultaneous occurrences of histologically distinct benign and malignant tumors were identified. Retrospective analysis demostrated that there was a decreasing risk gradient for multiple tumors of the reproductive systems. The intact female had the highest risk followed in order by the spayed female and all male dogs. The incidence-based analyses also indicated a strong predilection for development of multiple tumors within both the female and the male reproductive systems. A four- to five-fold increase in observed numbers of mammary tumors and other histologically distinct reproductive tumors was found. Benign and malignant mammary tumors were strongly associated in their occurrence, and dogs with benign mammary neoplasms had a three-fold increased risk for subsequent development of histologically different malignant mammary tumors. These quantitative results were consistent with observations in man for malignancies and provide additional evidence that multiple primary malignant and benign neoplasms of the female and male reproductive systems are biologically associated.     

The Prognostic Significance of Angiogenesis in Canine Mammary Tumors

The purpose of the study was to determine if neovascularization, a measure of angiogenesis, is correlated with metastasis of mammary tumors in dogs. Forty-six paraffin-embedded tissue blocks of benign and malignant canine mammary tumors obtained from 42 clinical cases at the Iowa State University Veterinary Teaching Hospital were retrieved from the archives of the Department of Veterinary Pathology. Of the dogs with malignant tumors, cases with and without lymph node metastasis were chosen. Neovascularization was quantified by light microscopy on formalin-fixed, paraffin-embedded sections of canine mammary tumors using an avidin biotin immunoperoxidase assay for factor VIII-related antigen. Mean microvessel counts for each group were statistically evaluated using analysis of variance. The mean number of microvessels was highest in the malignant tumors of dogs with lymph node metastasis (44). This number was significantly different from the mean number of microvessels in the benign tumors (28; P = .03) and a trend occurred toward higher microvessel counts in malignant tumors with lymph node metastasis versus malignant tumors of dogs without metastasis (32; P = .1). No significant difference was found between the number of microvessels found in malignant tumors without metastasis versus benign tumors. The trend toward higher microvessel counts in mammary tumors that have metastasized supports the premise that angiogenesis may be an independent and significant prognostic indicator in dogs with malignant mammary tumors, as it is in women with breast cancer.     

Correlation between the histopathological diagnosis by AgNOR count and AgNOR area in canine mammary tumors

Background: Mammary tumors are the most common type of tumor in female dogs. The histopathological diagnosis is usually made by a hematoxylin-eosin (HE) staining of the tumor, which then requires a pathologist's judgment for assessment of malignancy. The purpose of this study was to investigate an alternative silver staining of some argyrophilic nucleolar organizer regions (AgNOR) for improving the diagnostic accuracy with mammary tumors.
Hypothesis: There is a correlation between the histopathological diagnosis by AgNOR count and AgNOR area in canine mammary tumors.
Animals: Seventy-three canine mammary tumors from 33 female dogs.
Materials and Methods: The AgNOR staining was evaluated retrospectively in 73 canine mammary tumors with a parallel HE staining as a "Gold Standard." Both a quantitative manual counting method and a qualitative computerized morphometric method were tested.
Result: The result from both methods indicated a clinically relevant difference in the mean values of the AgNOR in the following 4 categories: malignant, benign, hyperplastic, and normal mammary tissue. The counting method was superior, with 89% of the cases given a correct diagnosis of a malignant or a nonmalignant canine mammary tumor. The 2 methods were then compared to test their ability to classify the tumors correctly. Again, the counting method was the most reliable method, with a sensitivity of 80% and a specificity of 76% when the upper 50% of the AgNOR counts were presumed malignant.
Conclusion and Clinical Importance: The results indicated that an AgNOR test could be an aid to pathologists as a prognostic indicator or to assist them in deciding between a benign or a malignant diagnosis in questionable cases.     

Frequency of canine and feline tumors in a defined population.

The Tulsa Registry of Canine and Feline Neoplasms was the second animal tumor registry in the United States concerned with a defined population in a delimited geographic area. Only tumors histologically confirmed by registry pathologists were included in frequency statistics based on the annual dog and cat population presented to veterinarians. During the first registry year, about 1% of the 63,504 dogs and 0.5% of the 11,909 cats had one or more primary tumors. While the incidence rate for malignant tumors in dogs was similar to that in cats, the incidence of benign tumors of dogs was over 10 times that of cats. The most common tumors were sebaceous adenoma in dogs and lymphosarcoma in cats. Mammary cancer was the most common malignant tumor in dogs. Mammary tumors of female dogs were significantly more frequent in Pointers, Poodles and Boston Terriers, in that order, than in other breeds. A greater incidence of mammary tumors among intact compared to spayed female dogs was seen for virtually every age group except in the Pointer breed.     

The activity of matrix metalloproteinases (MMPS) and tissue inhibitors of metalloproteinases (TIMPs) in mammary tumors of dogs and rats

We conducted zymography for detecting the activity of matrix metalloproteinases (MMPs) and reverse zymography for the activity of tissue inhibitors of metalloproteinases (TIMPs) in canine spontaneous and rat 7, 12-dimethylbenz(a)anthracene (DMBA)-induced mammary tumor tissues. The activities of MMPs of canine mammary tumors were quite higher than those of the rat chemically induced tumors. The activities of MMPs were significantly higher in malignant tissues than in benign ones of canine tumors, whereas the activity of only MMP-2 was higher in both benign and malignant rat tumors compared to normal tissues. There were no differences of MMPs activities between benign and malignant rat tumors. The results of reverse zymography indicated that the activities of TIMP-1, -2 and -3 were strikingly higher in rat tumors than in canine tumors. The activities were higher in malignant tissues than in benign ones of dogs, and higher in tumor tissues than in normal mammary tissues of rats. The results of film in situ zymography for tissue localization of gelatinolytic activity showed that the digested area was more extended in malignant tumors than in benign ones of dogs. However, the area was similarly extended in both benign and malignant rat tumors. These results may indicate that the canine spontaneous malignant mammary tumors possess more aggressive nature than the rat chemically induced counterpart, resulting from the high level of MMPs and low level of TIMPs activities of the tumor tissues.     

Mammary tumors in a colony of beagle dogs

In a lifetime study, female beagle dogs in a closed colony were administered 226radium and 90strontium. An unirradiated control group was included in the study. A total of 223 of 356 dogs at risk developed 1,112 mammary proliferative growths (hyperplastic nodules and neoplasms). There was no correlation between occurrence and types of lesions in radiation and control groups. The age range for first occurrence of lesions was 10.4 to 13.9 years; hyperplastic nodule and benign mixed tumor occurred 1 to 2 years earlier than other lesions. A multiplicity of growths of similar or different morphological type were common throughout the lifetime of the dog. The female beagles, collectively, developed 244 hyperplastic nodules, 78 adenomas, 694 benign mixed tumors, 78 carcinomas, 14 malignant mixed tumors, and four myoepitheliomas. Proliferations occurred with increasing frequency from the cranial to caudal mammary glands. Metastasis was found in 77% of the dogs with carcinoma. The median time from diagnosis to metastasis was 10 months, but was shorter in dogs with infiltrative carcinoma.     

Immunohistochemistry for parathyroid hormone-related protein (PTHrP) in benign and malignant mammary mixed tumors of dogs with and without hypercalcemia

We evaluated the expression of parathyroid hormone-related protein (PTHrP) by immunohistochemistry in eight benign and malignant mammary mixed tumors of dogs with (n = 4) and without (n = 4) hypercalcemia. Positive immunoreactive staining for PTHrP was observed in all four tumors from hypercalcemic dogs. The mammary tumors from 2 of the 4 normocalcemic dogs stained positively for PTHrP, but the numbers of immunoreactive cells and intensity of the immunoreaction were less than in the hypercalcemic dogs. In the other 2 tumors without hypercalcemia, the tissue samples were negative for PTHrP.     

Serum alkaline phosphatase isoenzyme activities in canine malignant mammary neoplasms with and without osseous transformation

BACKGROUND: Increased serum activity of total alkaline phosphatase (TALP) has been found in dogs with mammary neoplasms, especially malignant mixed tumors. We hypothesized that the bone isoenzyme of alkaline phosphatase (BALP), a specific indicator of osteoblastic activity and bone formation, may contribute to increased TALP in dogs with mammary neoplasms with osseous transformation. OBJECTIVE: The purpose of this study was to compare serum TALP, BALP, and other ALP isoenzyme activities in dogs with mammary malignant neoplasms with and without osseous transformation. METHODS: Twenty-one female dogs with malignant mammary neoplasms were compared with 21 clinically healthy, age-matched female control dogs. Physical, clinicopathologic (including preprandial and postprandial serum bile acids, ACTH stimulation, and low-dose dexamethasone suppression tests), radiographic, and ultrasonographic examinations were performed on all dogs with tumors to assess coexisting conditions. On the basis of histologic examination of excised tumors, dogs were further classified as having epithelial (n = 11) or mesenchymal/mixed (epithelial-mesenchymal) (n = 10) neoplasms, the latter of which had histologic and radiologic evidence of bone formation. Serum TALP, BALP, liver alkaline phosphatase (LALP), and corticosteroid-induced alkaline phosphatase (CALP) activities were measured using biochemical methods. RESULTS: Dogs with malignant mammary tumors had significantly higher (P < .05) median serum TALP (170 U/L), BALP (59 U/L), LALP (49 U/L), and CALP (24 U/L) activities, compared with control dogs (81, 32, 37, and 5 U/L, respectively). Significantly higher activities of BALP and LALP were found in dogs with epithelial neoplasms; whereas, only CALP activity was higher in dogs with mesenchymal/mixed neoplasms. There was no significant difference in TALP or isoenzyme activitities between epithelial and mesenchymal/mixed groups. CONCLUSION: BALP activity is increased in some dogs with malignant mammary tumors but does not account for the increase in TALP in dogs with neoplasms that have osseous transformation.     

Canine mammary gland tumours; a histological continuum from benign to malignant; clinical and histopathological evidence*

This study describes the clinical and histopathological findings in dogs with mammary gland tumours, and compares the histopathological and clinical evidence consistent with progression from benign to malignant to human breast cancer epidemiology. Clinical and histopathological data on 90 female dogs with 236 tumours was included. Dogs with malignant tumours were significantly older than dogs with benign tumours (9.5 versus 8.5 years), P = 0.009. Malignant tumours were significantly larger than benign tumours (4.7 versus 2.1 cm), P = 0.0002. Sixty‐six percent had more than one tumour, and evidence of histological progression was noted with increasing tumour size. Dogs with malignant tumours were significantly more likely to develop new primary tumours than dogs with benign tumours, P = 0.015. These findings suggest that canine mammary tumours progress from benign to malignant; malignant tumours may be the end stage of a histological continuum with clinical and histopathological similarities to human breast carcinogenesis.     

p53 gene mutations occurring in spontaneous benign and malignant mammary tumors of the dog

Sixty-three cases of benign and malignant canine mammary tumors were analyzed to define the alteration of exons 5-8 for the p53 tumor suppressor gene using polymerase chain reaction direct sequence analysis with paraffin-embedded tissues. Four missense mutations were found in 38 benign mammary tumors (11%), and five missense (one tumor had two missense mutations) and one nonsense mutations were found in 25 mammary carcinomas (20%). These data suggest that the p53 gene alterations might be initiated at an early stage of canine mammary carcinogenesis and p53 mutations might be associated with malignancy. However, there was no evidence of any relationship between the p53 alterations and the histologic types of tumors or breeds of dogs.     

Prognostic factors associated with survival two years after surgery in dogs with malignant mammary tumors: 79 cases (1998-2002)

OBJECTIVE: To identify prognostic factors for female dogs that have undergone surgical removal of malignant mammary tumors. DESIGN: Retrospective case series. ANIMALS: 79 female dogs with malignant mammary tumors. PROCEDURE: Information obtained from the medical records included breed, age, sex, tumor size (maximum diameter), number and location of affected mammary glands, time between tumor identification and surgical removal, radiographic evidence of distant metastasis, surgical procedure, ovariohysterectomy (OHE) status, histologic classification of the tumor, and survival time. RESULTS: Results of univariate analyses indicated that clinical stage, tumor size, OHE status, metastasis to adjacent lymph nodes or distant sites, and histologic classification of the tumor were significantly associated with survival 2 years after surgery. Tumors > or = 5 cm in diameter and tumors that had been identified > 6 months before surgery were more likely to metastasize to adjacent lymph nodes. Ovariohysterectomy was more beneficial in dogs with complex carcinomas than in dogs with simple carcinomas. In multivariate analyses, clinical stage, tumor size, and OHE status were significantly associated with survival 2 years after surgery. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that tumor stage, tumor size, and OHE status were significant prognostic factors associated with survival 2 years after surgery in dogs with malignant mammary tumors. Further, either dogs with tumors > or = 5 cm in diameter or dogs with tumors present for > 6 months prior to surgery had a higher risk of having lymph node metastases.     

Immunohistochemical analysis of cyclin A, cyclin D1 and P53 in mammary tumors, squamous cell carcinomas and basal cell tumors of dogs and cats

The involvement of cyclin A, cyclin D1 and p53 proteins in canine and feline tumorigenesis was analyzed immunohistochemically. In the present study, a total of 176 cases were examined, among which there were 108 canine cases (75 mammary lesions, 16 squamous cell carcinomas and 17 basal cell tumors) and 68 feline cases (43 mammary lesions, 20 squamous cell carcinomas and 5 basal cell tumors). Speckled nuclear staining for cyclin A was observed in 19/38 (50%) canine malignant mammary tumors and 18/37 (48.6%) feline mammary carcinomas, while this was not seen in benign mammary tumors of either dogs or cats. Marked intense nuclear cyclin A staining was seen in 7/16 (43.8%) canine squamous cell carcinomas and 18/20 (90.0%) feline squamous cell carcinomas. Only 3/17 (17.6%) canine basal cell tumors showed slight and scattered staining for cyclin A. Expression of cyclin D1 was very rare in both canine and feline tumors. Nuclear staining of p53 was found in 7/37 (18.9%) feline mammary carcinomas. Intense immunoreactivity for p53 was found in 6/16 (37.5%) canine squamous cell carcinomas and 8/20 (40%) feline squamous cell carcinomas. These results suggest that cyclin A may have a role in the proliferation of canine malignant mammary tumors, feline mammary carcinomas and squamous cell carcinomas of dogs and cats, and p53 may associate with the tumorigenesis of feline mammary carcinomas and squamous cell carcinomas of dogs and cats.     

Canine mammary tumours: protective effect of late ovariectomy and stimulating effect of progestins

Ovariectomy, even when performed at an advanced age, was found to be to some extent protective against mammary tumour development in dogs. Bitches treated with progestins had a slightly higher risk for mammary tumours (all types, benign and malignant) than controls. Progestin treatment did not increase the risk of mammary cancer. Benign tumours in (treated and untreated) dogs appeared earlier than malignant ones. Progestin treatment resulted in earlier appearance of both benign and malignant tumours than in controls. The ratio solitary/multiple mammary tumours was not significantly different between treated and untreated dogs.     

Cyclooxygenase-2 expression in canine mammary tumors

Mammary tumors are the most common neoplasms in female dogs. Induction of cyclooxygenase-2 (COX-2) has been implicated in various cancers in humans. However, expression of COX-2 has not been investigated in canine mammary tumors. Normal mammary gland (n = 4), simple or complex adenomas (n = 63), and simple or complex adenocarcinomas (n = 84) were studied by immunohistochemistry. Results showed that COX-2 was not expressed in the normal gland but was detected in 24% of adenomas and in 56% of adenocarcinomas (P < 0.001). The incidence of COX-2 expression and the intensity of the COX-2 signal were higher in adenocarcinomas than in adenomas (P < 0.001). These results demonstrate for the first time that COX-2 is induced in a proportion of canine mammary tumors and that COX-2 expression is more frequent and more intense in malignant than in benign tumors, suggesting a potential role for COX-2 in canine mammary tumorigenesis.     

Mammary cancer in the dog: a study of 120 cases.

Of the 120 cases of mammary cancer occurring in 117 female dogs (15 spayed), 2 male dogs, and 1 dog of undetermined sex, 107 (nearly 90%) were observed in dogs 8 to 15 years old. Mammary tumors occurred in nearly 14% of 875 female dogs with neoplasms. Nearly 60% of 128 neoplasms were located in the 4th and 5th mammary glands. Of the 128 cancers in these 120 dogs, 85 were classified as duct carcinoma, 38 as lobular carcinoma, 3 as malignant mixed tumor, and 2 as duct and lobular carcinomas. Most duct carcinomas originated in the epithelial cells of ducts at all levels, and a few arose in previously benign duct papillomas. The lobular carcinomas arose in alveoli and developed into progressively larger lobules. A negative factor in the development of mammary cancer is ovariectomy before or shortly after the first estrous cycle in the dog and before the age of 40 in women. In both dog and man, aging is a positive factor in the development of mammary cancer. In women, other positive factors are nulliparity and inheritance; e.g., a high rate of breast cancer in close female relatives of Jewish extraction. An epidemiologic study of breast cancer in man and dog in high-risk countries(e.g., United States) and low-risk countries (e.g., Japan) is indicated.     

Cytologic examination of fine‐needle aspirates from mammary gland tumors in the dog: diagnostic accuracy with comparison to histopathology and association with postoperative outcome

Background: Mammary tumors are the most common neoplasms in female dogs. Malignant tumors may carry a poor prognosis and necessitate surgery. Few data are available on the value of cytologic examination as a diagnostic or prognostic tool for mammary tumors in dogs. Objectives: The objectives of this study were to determine whether cytologic findings in fine‐needle aspirate specimens of canine mammary tumors correlate with histopathologic results and whether the cytologic diagnosis is associated with postoperative outcome. Methods: In this prospective study, fine‐needle aspirate samples were obtained from 50 mammary tumors in 50 dogs. Results of cytologic and histopathologic examination were compared, using the histologic diagnosis as the reference method. Kaplan–Meier log rank analysis was used to evaluate univariate association of the cytologic diagnosis with duration of survival, local control, and metastasis‐free interval. Results: Adequate cytologic samples were obtained in 43/50 (86%) cases. The cytologic diagnosis correlated with the histologic diagnosis for benign and malignant tumors in 40/43 (93%) and 35/43 (81%) cases, respectively. Cytologic examination had a sensitivity of 88% and a specificity of 96% for the diagnosis of malignancy. The cytologic diagnosis had significant univariate association with duration of survival (P=.016), recurrence‐free interval (P=.003), and metastasis‐free interval (P=.014). Conclusions: Cytologic examination of mammary tumors in the dog has satisfactory accuracy, sensitivity, and specificity for the diagnosis of malignancy and is associated with postoperative outcome. Further studies on the diagnostic accuracy of cytology as well as multivariate analysis of its preoperative prognostic value in mammary tumors in the dog are warranted.     

GH-producing mammary tumors in two dogs with acromegaly

Two intact female dogs were admitted for growing mammary tumors. They had symptoms of acromegaly including weight gain, enlargement of the head, excessive skin folds, and inspiratory stridor. Serum concentrations of growth hormone (GH), insulin-like growth factor-I (IGF-I), and insulin were elevated in the two cases. From these findings, both dogs were diagnosed with acromegaly. In case 1, the GH, IGF-I, and insulin levels subsided after removal of the focal benign mammary tumors and ovariohysterectomy. In case 2, those levels subsided after removal of only focal mammary carcinoma. In both cases, immunohistochemical investigations for GH were positive in the mammary tumor cells but not in the normal mammary glands. We concluded that GH-producing mammary tumors caused the present acromegaly.     

Immunohistochemical study of hormonal receptors and cell proliferation in normal canine mammary glands and spontaneous mammary tumours

The expression of hormone receptors and their relationship to cell proliferation in six samples of normal canine mammary tissue, and 11 benign and 10 malignant mammary neoplasms from female dogs were assessed by immunohistochemistry in formalin-fixed paraffin-embedded samples, by using monoclonal antibodies against progesterone and oestrogen receptors, and nuclear antigen Ki-67 (MIB-1). Malignant tumours negative for progesterone receptors proliferated at higher rates than progesterone receptor-positive tumours, suggesting that the progression towards malignancy in spontaneous mammary tumours is accompanied by a decrease in hormonal steroid dependency. Only one malignant tumour was positive for oestrogen receptors.     

Serum neopterin levels in female dogs with malignant mammary tumours

In this study, we have determined serum neopterin levels in female dogs with primary malignant mammary tumours. The study involved 50 female dogs which had a malignant mammary tumours removed surgically (32 animals with carcinoma, 12 animals with sarcoma and 6 animals with carcinosarcoma) and 10 clinically healthy female dogs. Serum neopterin levels were determined using a commercial ELISA kit. The mean neopterin levels were lower in the malignant tumour groups than in healthy animals but differences were statistically significant only in carcinoma and sarcoma groups. The decrease of neopterin levels in animals with malignant mammary tumours may suggest their decreased cellular immunity. Moreover, it might indicate that decreased activity of cellular mechanisms of the anti‐neoplastic response is one of the factors associated with the development and course of malignant mammary tumours in female dogs; however, further studies are necessary.