Progesterone receptors in normal, dysplastic and tumourous feline mammary glands. Comparison with oestrogen receptors status

fHER2, PR, ER, Ki-67 and Cytokeratin 5/6 Expression in Benign Feline Mammary Lesions

Simple Summary

Feline mammary neoplasias are highly prevalent in domestic cats and present many similarities to their human counterparts. Since information about benign feline mammary lesions is still scarce and often controversial, studies using a wider panel of oncological biomarkers are necessary to understand their potential contribution to malignant lesions. This study analyzed 47 benign lesions from 27 queens, regarding the expression of estrogen and progesterone receptors (ER and PR, respectively), fHER2 protein and two malignancy indicators (Ki-67 and CK 5/6). Our results showed that most of the lesions were ER positive (91.5%), PR negative (63.8%), fHER2 negative (64.4%), Ck 5/6 negative (76.6%) and with a low Ki-67 index (78.7%). Additionally, significant correlations were found between younger ages and ER positivity and between larger lesions and negative PR status. Our results highlight the importance of estrogen receptors in the development of benign feline mammary lesions, further contributing to the development of preventive and monitoring strategies in feline mammary oncology.

Abstract

Biomarkers are essential in the characterization of neoplastic lesions and aid not only in the classification of the nature of the lesions, but also in the understanding of their ontogeny, development and prognosis. In cats, while mammary carcinomas are increasingly being characterized, information on their benign lesions is still scarce. Indeed, a better characterization of benign lesions could have an important role in unravelling mammary oncogenesis, similar to that in human breast cancer. Thus, in this study, the expression of five markers was analyzed in 47 benign mammary lesions (hyperplasia, dysplasia and benign tumors) collected from 27 queens. Dysplastic and hyperplastic lesions were the most common (41/47, 81.7%). Most of the lesions were classified as ER positive (43/47, 91.5%), PR negative (30/47, 63.8%), fHER2 negative (29/47, 64.4%), CK 5/6 negative (36/47, 76.6%) and with a low Ki-67 index (37/47, 78.7%). Statistical analysis revealed a correlation between younger ages and ER positivity (p = 0.013) and between larger lesions and negative PR status (p = 0.038). These results reinforce the importance of evaluating the expression of the ER status, prevalent in benign lesions, as a putative precursor in cancer progression.

Mammary Fibroadenoma in Cats: A Matter of Classification

Benign mammary lesions are infrequent in cats. Among these, the most common is feline fibroadenomatous change, a hyperplastic/dysplastic change associated with hormonal imbalances. Although never thoroughly described in scientific literature, feline fibroadenomas, which share some morphological features with fibroadenomatous change, have been variably included in classification systems. The aim of this study was to characterise feline mammary fibroadenomas from a histological and immunophenotypical point of view in order to allow the standardisation of classification. Nine cases were retrospectively collected from eight female and one male cat with no history of hormonal stimulation. Diagnostic inclusion criteria were defined and immunohistochemistry was performed. Histologically, nodules were composed of neoplastic epithelial cells arranged in arborizing lobular-like structures surrounded by abundant proliferating stroma. In all analysed cases, epithelial elements showed immunolabelling for pancytokeratin, cytokeratin19, and β-catenin. Interestingly, five cases showed multifocal epithelial vimentin positivity. Epithelial nuclear oestrogen receptor positivity was observed in three of the nine samples. In all cases, myoepithelial cells did not extend into the interstitium. Stromal cells expressed vimentin, calponin, and mild β-catenin. The median Ki67 scores were 18% and 8.3% in the epithelial and stromal components, respectively. This study describes, for the first time, the morphological and immunophenotypical features of feline mammary fibroadenoma, highlighting its existence as a separate entity from fibroadenomatous change.

VISTA Is a Diagnostic Biomarker and Immunotherapy Target of Aggressive Feline Mammary Carcinoma Subtypes

Simple Summary

Mammary tumors are common in cats, showing aggressive behavior and few therapeutic options. Recently, feline mammary carcinomas have become a reliable cancer model for human breast cancer studies, due to the similarities between the two species. Thus, the identification of new tumor biomarkers and therapeutic targets to improve cat’s prognosis is needed. VISTA is an important immune checkpoint protein that has gained importance over the past few years in women’s cancers. In this study, the serum VISTA levels and tumor expression were analyzed in cats with mammary tumors, being correlated with other immune checkpoints. In the diseased animals, VISTA is overexpressed in more aggressive tumor subtypes (HER2-positive and triple-negative), showing a positive correlation with the expression of VISTA in tumor-infiltrating lymphocytes, and is associated with an immunosuppressive status, suggesting that VISTA could be a promising non-invasive prognostic biomarker and therapeutic target in cats with mammary carcinomas, as reported in humans.

Abstract

Feline mammary carcinoma (FMC) is a common neoplasia, showing aggressive clinicopathological features, without viable therapeutic options. The study of tumor microenvironment has gained importance, due to the ability to control tumor progression by regulating the immune response. Considering the lack of knowledge, feline serum VISTA levels from cats with mammary carcinoma were compared with healthy controls, and with serum levels of PD-1/PD-L1, CTLA-4, LAG-3, IL-6, and TNF-α. In parallel, VISTA tumor expression was evaluated in FMC samples. The obtained data revealed that serum VISTA levels were significantly higher in cats presenting HER2-positive (p = 0.0025) or triple-negative subtypes (p = 0.0019), with higher serum levels in luminal A (p = 0.0025) correlated to the presence of metastasis (p = 0.0471). Furthermore, in HER2-positive or triple-negative tumors, correlations were obtained between serum VISTA levels and the serum levels of the above-mentioned molecules. In tumors, VISTA expression revealed a stronger intensity in cancer cells, when compared to TILs (p < 0.0001). Stratifying the samples by subtypes, a higher number of VISTA-positive TILs was observed in the HER2-positive subtype, compared with triple-negative tumors (p = 0.0138). In conclusion, results support the development of therapeutic strategies for HER2-positive and triple-negative FMC subtypes, reinforcing the use of cats as a human oncology model.

Gynaecomastia in a male neutered cat with an adrenal tumour and associated hyperprogesteronism, hypercortisolism and hyperaldosteronism

Case summary

A 7-year-old male neutered domestic longhair cat was presented with chronic progressive gynaecomastia, polydipsia, polyphagia, weight loss and poor fur regrowth. Sexualised behavioural changes were not reported and virilisation was not present on physical examination. Pertinent haematology, biochemistry and urinalysis findings at the time of referral included mild hypokalaemia. Left adrenomegaly and mild prostatomegaly were identified on a CT scan. Evaluation of adrenal hormones with a low-dose dexamethasone suppression test, serum progesterone, testosterone, oestradiol, plasma aldosterone, renin, plasma metanephrine and normetanephrine measurement supported a diagnosis of hyperprogesteronism, hyperaldosteronism and hypercortisolism. Adrenalectomy was performed and histopathology was consistent with an adrenocortical tumour. Clinical signs and hormone elevations resolved postoperatively.

Relevance and novel information

To our knowledge, this is the second report of gynaecomastia secondary to an adrenal tumour in a male neutered cat and the first associated with hyperprogesteronism.

Comparative mammary gland postnatal development and tumourigenesis in the sheep, cow, cat and rabbit: Exploring the menagerie

Sheep, cows, cats, and rabbits are kept by humans for agricultural purposes and as companion animals. Much of the mammary research in these species has focussed on mastitis in the case of ruminants and rabbits, and mammary tumourigenesis in cats and rabbits. However, similarities with the human breast suggest that these species may be currently underutilised as valuable comparative models of breast development and disease. The mammary gland undergoes cyclical postnatal development that will be considered here in the context of these non-traditional model species, with a focus on the mammary microenvironment at different postnatal developmental stages. The second part of this review will consider mammary tumour development. Ruminants are thought to be relatively 'resistant' to mammary tumourigenesis, likely due to multiple factors including functional properties of ruminant mammary stem/progenitor cells, diet, and/or the fact that production animals undergo a first parity soon after puberty. By contrast, unneutered female cats and rabbits have a propensity to develop mammary neoplasms, and subsets of these may constitute valuable comparative models of breast cancer.

Evaluation of prognostic factors and survival rates in malignant feline mammary gland neoplasms

OBJECTIVES

The aim of the study was to investigate prognostic factors in feline mammary gland neoplasms, correlating them with overall survival (OS).

METHODS

Fifty-six primary malignant mammary gland neoplasms and 16 metastatic lymph nodes from 37 female cats were analyzed. Clinical staging, histologic type and grade, and immunohistochemistry for Ki-67, progesterone and estrogen receptor, human epidermal growth factor receptor type 2 (HER-2), cyclooxygenase-2 (COX-2) and vascular endothelial growth factor (VEGF) were evaluated. Follow-up was performed in order to correlate prognostic factors with OS.

RESULTS

Lymph node metastasis was found in 35% of cases. Clinical stage III, tubulopapillary carcinomas and histologic grade II cases prevailed in the study. Most neoplasms were positive for hormonal receptors, negative for HER-2 overexpression and presented VEGF overexpression. Immunoreactivity for Ki-67 (P = 0.046) and COX-2 (P = 0.007) was higher in metastases than in primary tumors. COX-2 (P = 0.089), HER-2 (P = 0.012) and histologic grade (P = 0.080) were correlated with OS.

CONCLUSIONS AND RELEVANCE

The data suggest that inhibition of ovarian hormones and COX-2 may represent a therapeutic option for malignant feline mammary gland neoplasms. When evaluating disease progression, COX-2 scores and Ki-67 index should be analyzed in primary tumors and metastases. Histologic grade, HER-2 status and COX-2 scores were found to have a direct influence on OS. Prognostic factors allow for a better understanding of disease outcome in a condition that is characterized by a poor prognosis. The present work highlights the need for further studies on endocrine therapy and COX-2 inhibitors, which could influence OS.

CLINICOPATHOLOGIC FEATURES OF MAMMARY MASSES IN CAPTIVE LIONS (PANTHERA LEO)

A multi-institutional retrospective analysis of 330 pathology accessions from 285 different lions found 15 captive, female African lions (Panthera leo) with confirmed mammary masses. Aside from the presence of a mammary mass, the most common initial clinical sign was inappetence. Histologic diagnoses were predominantly adenocarcinoma (n = 12), though two benign masses (mammary hyperplasia and a mammary cyst) and one squamous cell carcinoma were identified. Nine of 13 malignant tumors had metastasized to lymph nodes or viscera at the time of necropsy. Six lions with adenocarcinoma and two lions with benign mammary masses had received hormonal contraception, though little evidence of mammary lobular hyperplasia was seen in association with the adenocarcinomas. The most common concurrent disease processes found at necropsy were chronic urinary tract disease and other malignancies. These cases demonstrate that mammary malignancies occur in captive lions and frequently metastasize.

Cats, Cancer and Comparative Oncology

Naturally occurring tumors in dogs are well-established models for several human cancers. Domestic cats share many of the benefits of dogs as a model (spontaneous cancers developing in an immunocompetent animal sharing the same environment as humans, shorter lifespan allowing more rapid trial completion and data collection, lack of standard of care for many cancers allowing evaluation of therapies in treatment-naïve populations), but have not been utilized to the same degree in the One Medicine approach to cancer. There are both challenges and opportunities in feline compared to canine models. This review will discuss three specific tumor types where cats may offer insights into human cancers. Feline oral squamous cell carcinoma is common, shares both clinical and molecular features with human head and neck cancer and is an attractive model for evaluating new therapies. Feline mammary tumors are usually malignant and aggressive, with the ‘triple-negative’ phenotype being more common than in humans, offering an enriched population in which to examine potential targets and treatments. Finally, although there is not an exact corollary in humans, feline injection site sarcoma may be a model for inflammation-driven tumorigenesis, offering opportunities for studying variations in individual susceptibility as well as preventative and therapeutic strategies.

Prognostic evaluation of feline mammary carcinomas: a review of the literature

A large number of studies have investigated feline mammary tumors in an attempt to identify prognostic markers and generate comparative analyses with human breast cancer. Nevertheless, a retrospective base of assessments and the lack of standardization in methodology and study design have caused weakness in study results, making comparison difficult. We examined feline mammary tumor publications and evaluated postulated prognostic parameters according to the recently published "Recommended Guidelines for the Conduct and Evaluation of Prognostic Studies in Veterinary Oncology." Using these criteria, we determined with statistically significant reliability that prognostic parameters for feline mammary tumors are tumor grading and lymph node/lymphovascular invasion. Furthermore, tumor subtype, size, and staging are worthy of further standardized investigation. We present statistical significance for each studied parameter as well as its relevance to disease progression and survival. Our evaluation suggests that marker expression (ie, Ki67, HER2, ER) may provide relevant information applicable for therapeutic predictions; however, consensus efforts and protocol standardization are needed. We identify and discuss major points of concern--such as sample preservation and selection, standardization of immunohistochemical protocols, and evaluation of results--to provide support for subsequent reliable analyses.

Mammary tumours in the cat: size matters, so early intervention saves lives

PRACTICAL RELEVANCE

Mammary tumours are among the most common neoplasms in both cats and dogs, but the prevalence of malignant histological types is far higher in cats (ratio of malignant:benign is at least 4:1).

CLINICAL CHALLENGES

The more aggressive nature of mammary neoplasia in cats poses challenges for management. Prognosis is affected by tumour size and, therefore, early recognition and treatment of mammary tumours is paramount. Although the primary tumour can be excised surgically, no studies have shown that chemotherapy significantly extends survival time; hence, metastatic spread remains an important clinical problem.

PATIENT GROUP

Mammary tumours usually affect older female cats, mainly entire females. Siamese and Oriental breeds may be predisposed. Male cats can develop mammary neoplasia, but this is rare.

EVIDENCE BASE

This review summarises the current literature relating to aetiology, pathology, presentation, diagnosis, staging, treatment and prognosis of feline mammary tumours.

Feline mammary basal-like adenocarcinomas: a potential model for human triple-negative breast cancer (TNBC) with basal-like subtype

Background

Breast cancer is one of the leading causes of cancer deaths. Triple-negative breast cancer (TNBC), an immunophenotype defined by the absence of immunolabeling for estrogen receptor (ER), progesterone receptor (PR) and HER2 protein, has a highly aggressive behavior. A subpopulation of TNBCs exhibit a basal-like morphology with immunohistochemical positivity for cytokeratins 5/6 (CK5/6) and/or epidermal growth factor receptor (EGFR), and have a high incidence of BRCA (breast cancer susceptibility) mutations. Feline mammary adenocarcinomas (FMAs) are highly malignant and share a similar basal-like subtype. The purpose of this study was to classify FMAs according to the current human classification of breast cancer that includes evaluation of ER, PR and HER2 status and expression of basal CK 5/6 and EGFR. Furthermore, we selected triple negative, basal-like FMAs to screen for BRCA mutations similar to those described in human TNBC.

Methods

Twenty four FMAs were classified according to the current human histologic breast cancer classification including immunohistochemistry (IHC) for ER, PR HER2, CK5/6 and EGFR. Genetic alteration and loss of heterozygosity of BRCA1 and BRCA2 genes were analyzed in triple negative, basal-like FMAs.

Results

IHC for ER, PR and HER2 identified 14 of the 24 (58%) FMAs as a triple negative. Furthermore, 11of these 14 (79%) triple negative FMAs had a basal-like subtype. However, no genetic abnormalities were detected in BRCA1 and BRCA2 by direct sequencing and loss of heterozygosity analysis.

Conclusion

FMAs are highly aggressive neoplasms that are commonly triple negative and exhibit a basal-like morphology. This is similar to human TNBC that are also commonly classified as a basal-like subtype. While sequencing of a select number of triple negative, basal-like FMAs and testing for loss of heterozygosity of BRCA1 and BRCA2 did not identify mutations similar to those described in human TNBC, further in-depth evaluation is required to elucidate a potential role of BRCA in the tumorigenesis of triple negative, basal-like FMAs. The strong similarities in clinical behavior, morphology and IHC phenotype suggest that triple negative, basal-like FMAs may be a suitable spontaneous animal model for studying novel therapeutic approaches against human basal-like TNBC.

Activation of mammalian target of rapamycin (mTOR) in triple negative feline mammary carcinomas

Background

Triple negative breast cancer (TNBC) in humans is defined by the absence of oestrogen receptor (ER), progesterone receptor (PR) and HER2 overexpression. Mammalian target of rapamycin (mTOR) is overexpressed in TNBC and it represents a potential target for the treatment of this aggressive tumour. Feline mammary carcinoma (FMC) is considered to be a model for hormone-independent human breast cancer. This study investigated mTOR and p-mTOR expression in FMC in relation to triple negative (TN) phenotype.

Results

The expression of mTOR, p-mTOR, ERα, PR and HER2 was evaluated in 58 FMCs by immunohistochemistry and in six FMC cell lines by Western blot analysis. 53.5% of FMC analyzed were ER, PR, HER2 negative (TN-FMC) while 56.9% and 55.2% of cases expressed mTOR and p-mTOR respectively. In this study we found that m-TOR and p-mTOR were more frequently detected in TN-FMC and in HER2 negative samples.

Conclusions

In this study, we demonstrate that there is also a FMC subset defined as TN FMC, which is characterised by a statistically significant association with m-TOR and p-mTOR expression as demonstrated in human breast cancer.

Reduced expression of E-cadherin and β-catenin and high expression of basal cytokeratins in feline mammary carcinomas with regional metastasis

Feline mammary carcinomas are highly aggressive neoplasms. Several mechanisms are thought to be involved in their progression, including the loss of epithelial adhesion molecules. The present study was carried out on 21 adenomas and 139 mammary carcinomas. Of the carcinomas, 66 were not reported to have metastasized, while the remaining 73 had evidence of regional lymph node metastasis at the moment of diagnosis. The relationship was examined between the expression of the E-cadherin-β-catenin complex and basal (CK5/6, CK14) and luminal (CK8/18) cytokeratin expression. In the medical literature, carcinomas expressing basal cytokeratins are reported as having a poor prognosis in human breast cancer. Results revealed that preservation of the expression of E-cadherin and β-catenin is a significant feature of carcinomas without metastasis, whereas carcinomas with metastasis reveal the loss of one or both adhesion molecules. Additionally, basal cytokeratin expression was statistically associated with the presence of regional metastasis. Furthermore, the expression of E-cadherin-β-catenin was significantly correlated with the high expression of CK18 and low expression of CK5/6.

Spontaneous feline mammary intraepithelial lesions as a model for human estrogen receptor- and progesterone receptor-negative breast lesions

Background

Breast cancer is the most frequently diagnosed cancer in women. Intraepithelial lesions (IELs), such as usual ductal hyperplasia (UH), atypical ductal hyperplasia (ADH), and ductal carcinoma in situ (DCIS) are risk factors that predict a woman's chance of developing invasive breast cancer. Therefore, a comparative study that establishes an animal model of pre-invasive lesions is needed for the development of preventative measures and effective treatment for both mammary IELs and tumors. The purpose of this study was to characterize the histologic and molecular features of feline mammary IELs and compare them with those in women.

Methods

Formalin-fixed, paraffin-embedded specimens (n = 205) from 203 female cats with clinical mammary disease were retrieved from the archives of the Purdue University Animal Disease Diagnostic Laboratory and Veterinary Teaching Hospital (West Lafayette, IN), and the Department of Pathology and Veterinary Clinic, School of Veterinary Medicine (Sassari, Italy). Histologic sections, stained with hematoxylin and eosin (HE), were evaluated for the presence of IELs in tissue adjacent to excised mammary tumors. Lesions were compared to those of humans. Immunohistochemistry for estrogen receptor (ER-alpha), progesterone receptor (PR), human epidermal growth factor receptor 2 (HER-2/neu) and Ki-67 was performed in IELs and adjacent tumor tissues.

Results

Intraepithelial lesions were found in 57 of 203 (28%) feline mammary specimens and were categorized as UH (27%), ADH (29%), and DCIS (44%). Most IELs with atypia (ADH and DCIS) were associated with mammary cancer (91%), whereas UH was associated with benign lesions in 53% of cases. Feline IELs were remarkably similar to human IELs. No ER or PR immunoreactivity was detected in intermediate-grade or high-grade DCIS or their associated malignant tumors. HER-2 protein overexpression was found in 27% of IELs.

Conclusion

The remarkable similarity of feline mammary IELs to those of humans, with the tendency to lose hormone receptor expression in atypical IELs, supports the cat as a possible model to study ER- and PR-negative breast lesions.

The normal genital tract of the female California sea lion (Zalophus californianus): cyclic changes in histomorphology and hormone receptor distribution

Changes in reproductive tract histomorphology, and estrogen (ERalpha) and progesterone receptor (PR) expression throughout the breeding cycle were evaluated in free-ranging stranded female California sea lions (Zalophus californianus). Hormone receptor expression in the ovaries, uterus, cervix, and vagina was evaluated using an immunohistochemical technique with monoclonal antibodies. During a large portion of the cycle, ovaries contained both a corpora lutea (CL) and follicles in varying stages of development. In the periods of pupping and estrus during June and July, and in the spring morphologic features of the endometrium suggested estrogen influence. There were areas of squamous differentiation in the pseudostratified columnar epithelium of the cervix and vagina in some animals during estrus and in the spring. Estrogen receptor immunohistochemical scores were highest during pupping and estrus and in the spring and lowest during embryonic diapause. Cyclic changes in uterine PR expression throughout the cycle were minimal. Both ERalpha and PR were expressed in epithelial and stromal cells throughout the cervix and vagina, however, receptor expression was typically higher in the stroma. Stromal cell hormone receptors may play an important role in epithelial responses to circulating sex hormones. The results of this investigation add to the general knowledge of California sea lion reproduction and establish baseline information on reproductive tract hormone receptors that will aid in determining the factors involved in urogenital cancer development in sea lions.

Normal morphology and hormone receptor expression in the male California sea lion (Zalophus californianus) genital tract

Histomorphology and estrogen alpha (ER alpha), and progesterone receptor (PR) expression were evaluated in free-ranging stranded male California sea lions (Zalophus californianus). Hormone receptor expression was evaluated using an immunohistochemical technique with monoclonal antibodies. Estrogen and PRs were identified in the efferent ductules, prostate gland, corpus cavernosa, corpus spongiosium, penile urethra, and in the epithelium and stroma of both the penis and prepuce. In some tissues, ER alpha expression was more intense in the stroma, emphasizing the importance of the stroma in hormone-mediated growth and differentiation of reproductive organs. To our knowledge, this is the first study to localize ER alpha and PR to the epithelium of the glans penis. The results of this investigation add to the general knowledge of male California sea lion reproduction and suggest that estrogens could have a role in the function of the male reproductive tract.

Immunohistochemical expression of TopBP1 in feline mammary neoplasia in relation to histological grade, Ki67, ERα and p53

The immunohistochemical expression of topoisomerase IIbeta binding protein 1 (TopBP1) was examined in 123 feline mammary lesions (18 non-neoplastic lesions including six fibroadenomatous hyperplasia and 12 duct ectasia, 17 adenomas and 88 carcinomas) in relation to histological grade, oestrogen receptor alpha (ERalpha) status, proliferation index (Ki67) and p53 expression. There was positive staining for TopBP1 in 122 of 123 feline mammary lesions, although nine samples had fewer than 20% positive cells. The percentage of cells positive for TopBP1 increased with histological grade. Most staining was nuclear but both nuclear and cytoplasmic staining was observed as the degree of malignancy increased. TopBP1 is expressed in feline mammary tumours and its expression is correlated with histological grade. Many neoplasms which over-express p53 or are ERalpha negative show TopBP1 immunoreactivity.

Proto-oncogene HER-2 in normal, dysplastic and tumorous feline mammary glands: an immunohistochemical and chromogenic in situ hybridization study

Background

Feline mammary carcinoma has been proposed as a natural model of highly aggressive, hormone-independent human breast cancer. To further explore the utility of the model by adding new similarities between the two diseases, we have analyzed the oncogene HER-2 status at both the protein and the gene levels.

Methods

Formalin-fixed, paraffin-embedded tissue samples from 30 invasive carcinomas, 7 benign lesions and two normal mammary glands were analyzed. Tumour features with prognostic value were recorded. The expression of protein HER-2 was analyzed by immunohistochemistry and the number of gene copies by means of DNA chromogenic in situ hybridization.

Results

Immunohistochemical HER-2 protein overexpression was found in 40% of feline mammary carcinomas, a percentage higher to that observed in human breast carcinoma. As in women, feline tumours with HER-2 protein overexpression had pathological features of high malignancy. However, amplification of HER-2 was detected in 16% of carcinomas with protein overexpression, a percentage much lower than that observed in their human counterpart.

Conclusion

Feline mammary carcinoma would be a suitable natural model of that subset of human breast carcinomas with HER-2 protein overexpression without gene amplification.

Comparison of steroid receptor expression in normal, dysplastic, and neoplastic canine and feline mammary tissues

Steroid receptor expression was assessed by immunohistochemistry in neoplastic, hyperplastic/dysplastic, and normal mammary tissue samples removed from 68 queens and 47 bitches, using monoclonal antibodies against human oestrogen-alpha (ER) and progesterone receptors (PR). Mammary lesions were classified according to World Health Organization (WHO) criteria, and all animals with invasive carcinomas were clinically followed for 2 years. Stromal and/or lymphatic invasion and histological grading were also recorded. In both species, ER expression was significantly higher in healthy tissues, hyperplastic/dysplastic lesions, and benign tumours than in carcinomas. The loss of ER expression was more marked in feline than in canine carcinomas. In queens, PR expression increased in dysplastic lesions and "in situ" carcinomas and decreased in invasive carcinomas, even if parts of these tumours were still PR-positive. In bitches no significant variation in PR expression was observed between normal tissue, dysplasias, and benign neoplasms, but was significantly lower in carcinomas. In both species ER and PR expression in invasive carcinomas did not correlate either with histological parameters or overall survival time. This study demonstrates several differences in steroid hormone dependency between the two species. The percentage of PR-positive feline carcinomas suggests a possible role of progesterone in promoting early tumour cell growth in queens. The low percentage of ER-positive invasive carcinomas further demonstrated the aggressive phenotype and behaviour of feline mammary tumours.

A prospective analysis of immunohistochemically determined estrogen receptor alpha and progesterone receptor expression and host and tumor factors as predictors of disease-free period in mammary tumors of the dog

The immunohistochemically determined estrogen receptor (ER) alpha (ERalpha) and progesterone receptor (PR) status, as well as recognized, well-accepted prognostic indicators and host factors were prospectively analyzed in 84 cases of primary canine mammary carcinoma for their effect on disease-free period (recurrence free, metastasis free, or combined) (DFP) after an observation period of 18 months. The presence of one or both receptors, as well as tumor size, lymph node status, histologic grading, intravascular growth, and necrosis, were of prognostic value for DFP. In multivariate analysis, only tumor size and histologic grading proved to be independent prognosticators. None of the host factors analyzed were of prognostic value for DFP. ERalpha, PR, or both were detected in 173 out of 228 tumors: 70 ERalpha and PR; 5 ERalpha only; 98 PR only. Statistically significant differences regarding the presence of one or both receptors were observed between benign and malignant tumors and between complex, mixed, and simple histologic subtypes of benign and malignant tumors. In the group of malignant tumors (n=155), the presence of one or both receptors was more frequent in tumors smaller than 3 cm, without lymph node metastasis, with tubulopapillary rather than solid patterns of growth among simple carcinomas, of histologic grades I and II, without both intravascular growth and necrosis, and with lymphocyte cell infiltrates. The most frequent groups of hormone receptors-positive tumors were the ERalpha-positive and PR-positive group among benign and the ERalpha-negative and PR-positive group among malignant tumors.

Spontaneous Feline Mammary Carcinoma Is a Model of HER2 Overexpressing Poor Prognosis Human Breast Cancer

Companion animal spontaneous tumors are suitable models for human cancer, primarily because both animal population and the tumors are genetically heterogeneous. Feline mammary carcinoma (FMC) is a highly aggressive, mainly hormone receptor–negative cancer, which has been proposed as a model for poor prognosis human breast cancer. We have identified and studied the feline orthologue of the HER2 gene, which is both an important prognostic marker and therapeutic target in human cancer. Feline HER2 (f-HER2) gene kinase domain is 92% similar to the human HER2 kinase. F-HER2–specific mRNA was found 3- to 18-fold increased in 3 of 3 FMC cell lines, in 1 of 4 mammary adenomas and 6 of 11 FMC samples using quantitative reverse transcription-PCR. Western blot showed that an anti-human HER2 antibody recognized a protein comigrating with the human p185HER2 in FMC cell lines. The same antibodies strongly stained 13 of 36 FMC archival samples. These data show that feline HER2 overexpression qualifies FMC as homologous to the subset of HER2 overexpressing, poor prognosis human breast carcinomas and as a suitable model to test innovative approaches to therapy of aggressive tumors.

Immunohistochemical expression of progesterone receptors, growth hormone and insulin growth factor-I in feline fibroadenomatous change

The immunohistochemical expression, tissue-specific and cell-specific distribution patterns of progesterone receptors (PR), growth hormone (GH) and insulin growth factor-I (IGF-I) have been studied in 22 cases of feline fibroadenomatous change (FFAC). PR and GH were detected in all cases and were distributed homogeneously throughout the lesion, while IGF-I was detected in 77% of the cases at the site of ductal budding. The simultaneous expression of PR, GH and IGF-I was detected in epithelial cells in 14 of 22 cases while PR and GH expression only was detected in epithelial cells in 11 cases. Cases that expressed GH and IGF-I without PR expression in the stroma were the most numerous. Double immunohistochemical staining showed the co-localisation of PR and GH in a subset of ductal epithelial cells located between basal/myoepithelial and luminal cells (probably undifferentiated stem cells). These results suggest that ligand-activated progesterone receptors may induce the local synthesis of GH which in turn may exert its proliferative action directly and also indirectly through the production of other growth factors, such as IGF-I, in an autocrine/paracrine manner.