Prevalence and Classification of Spontaneous Mammary Intraepithelial Lesions in Dogs Without Clinical Mammary Disease

Three-Dimensional Cultivation a Valuable Tool for Modelling Canine Mammary Gland Tumour Behaviour In Vitro

Cell cultivation has been one of the most popular methods in research for decades. Currently, scientists routinely use two-dimensional (2D) and three-dimensional (3D) cell cultures of commercially available cell lines and primary cultures to study cellular behaviour, responses to stimuli, and interactions with their environment in a controlled laboratory setting. In recent years, 3D cultivation has gained more attention in modern biomedical research, mainly due to its numerous advantages compared to 2D cultures. One of the main goals where 3D culture models are used is the investigation of tumour diseases, in both animals and humans. The ability to simulate the tumour microenvironment and design 3D masses allows us to monitor all the processes that take place in tumour tissue created not only from cell lines but directly from the patient's tumour cells. One of the tumour types for which 3D culture methods are often used in research is the canine mammary gland tumour (CMT). The clinically similar profile of the CMT and breast tumours in humans makes the CMT a suitable model for studying the issue not only in animals but also in women.

Canine Mammary Tumor Histopathological Image Classification via Computer-Aided Pathology: An Available Dataset for Imaging Analysis

Histopathology, the gold-standard technique in classifying canine mammary tumors (CMTs), is a time-consuming process, affected by high inter-observer variability. Digital (DP) and Computer-aided pathology (CAD) are emergent fields that will improve overall classification accuracy. In this study, the ability of the CAD systems to distinguish benign from malignant CMTs has been explored on a dataset-namely CMTD-of 1056 hematoxylin and eosin JPEG images from 20 benign and 24 malignant CMTs, with three different CAD systems based on the combination of a convolutional neural network (VGG16, Inception v3, EfficientNet), which acts as a feature extractor, and a classifier (support vector machines (SVM) or stochastic gradient boosting (SGB)), placed on top of the neural net. Based on a human breast cancer dataset (i.e., BreakHis) (accuracy from 0.86 to 0.91), our models were applied to the CMT dataset, showing accuracy from 0.63 to 0.85 across all architectures. The EfficientNet framework coupled with SVM resulted in the best performances with an accuracy from 0.82 to 0.85. The encouraging results obtained by the use of DP and CAD systems in CMTs provide an interesting perspective on the integration of artificial intelligence and machine learning technologies in cancer-related research.

Rapid Evaporative Ionization Mass Spectrometry-Based Lipidomics for Identification of Canine Mammary Pathology

The present work proposes the use of a fast analytical platform for the mass spectrometric (MS) profiling of canine mammary tissues in their native form for the building of a predictive statistical model. The latter could be used as a novel diagnostic tool for the real-time identification of different cellular alterations in order to improve tissue resection during veterinary surgery, as previously validated in human oncology. Specifically, Rapid Evaporative Ionization Mass Spectrometry (REIMS) coupled with surgical electrocautery (intelligent knife—iKnife) was used to collect MS data from histologically processed mammary samples, classified into healthy, hyperplastic/dysplastic, mastitis and tumors. Differences in the lipid composition enabled tissue discrimination with an accuracy greater than 90%. The recognition capability of REIMS was tested on unknown mammary samples, and all of them were correctly identified with a correctness score of 98–100%. Triglyceride identification was increased in healthy mammary tissues, while the abundance of phospholipids was observed in altered tissues, reflecting morpho-functional changes in cell membranes, and oxidized species were also tentatively identified as discriminant features. The obtained lipidomic profiles represented unique fingerprints of the samples, suggesting that the iKnife technique is capable of differentiating mammary tissues following chemical changes in cellular metabolism.

Canine and feline in situ mammary carcinoma: A comparative review

Carcinoma in situ of the breast is a well-known entity in humans. In veterinary medicine, particularly in canine and feline mammary literature, there is no agreement whether the term in situ should be used to indicate a specific carcinoma histotype or the noninvasive status of a carcinoma of any histotype. Moreover, in the most recent histologic classification of mammary tumors published by the Davis-Thompson Foundation, it is suggested to abandon the term carcinoma in situ given the lack of standardized criteria defining this entity, replacing it with epitheliosis or ductal/lobular hyperplasia with severe atypia. This publication presents a critical review of the term in situ in human and veterinary medicine considering the evolution of the term over the years and its heterogeneous use by different authors, including variations in immunohistochemical markers for classification. This review aims to point out the lack of uniformity in the nomenclature and classification issues in veterinary medicine regarding the use of the term in situ, laying the ground for a process of standardization in future publications.

Epitheliosis is a histopathological finding associated with malignancy and poor prognosis in dogs with mammary tumors

Canine mammary epitheliosis (ME) is a poorly studied dysplasia that may have premalignant potential. In this study, the clinicopathological relevance of ME was prospectively studied in 90 female dogs with mammary tumors (MTs) that underwent radical mastectomy. ME distribution, extent, and coexistence with benign and malignant MTs were evaluated for each case (505 mammary glands). ME was macroscopically undetectable and was present in 47/90 (52%) cases, frequently bilateral. In dogs with malignant MTs and ME, diffuse ME throughout the mammary chain was present in 10/39 (26%) cases. A histological ME-carcinoma transition was evident in certain histotypes. By immunohistochemistry (AE1/AE3, cytokeratin 14 [CK-14], CK-8/18, vimentin, calponin, p63, Ki-67, estrogen receptor, progesterone receptor, and human epidermal growth factor receptor 2), ME was a slow-growing, triple-negative process with a strong predominance of basal-like nonmyoepithelial cells. ME was associated with older dogs (P = .016), malignant tumors (P = .044), worse clinical stages (P = .013), lymph node metastasis (LNM, P = .021), higher histological grade tumors (P = .035), and shorter overall survival (OS) in univariate analysis (P = .012). Interestingly, ME was distantly located to the malignant tumor in most cases (P = .007). In multivariate analyses, LNM (P = .005), histological grade (P = .006), and tumor size (P = .006) were independent predictors of OS. For the pathologist, the observation of ME should be clearly stated in the MT biopsy report to alert the surgeon/oncologist. Given the differences between canine ME and its human histopathological counterpart (atypical ductal hyperplasia), "epitheliosis" should remain the preferred term for the dog.

A Statistical Analysis of Risk Factors and Biological Behavior in Canine Mammary Tumors: A Multicenter Study

Canine mammary tumors (CMTs) represent a serious issue in worldwide veterinary practice and several risk factors are variably implicated in the biology of CMTs. The present study examines the relationship between risk factors and histological diagnosis of a large CMT dataset from three academic institutions by classical statistical analysis and supervised machine learning methods. Epidemiological, clinical, and histopathological data of 1866 CMTs were included. Dogs with malignant tumors were significantly older than dogs with benign tumors (9.6 versus 8.7 years, P < 0.001). Malignant tumors were significantly larger than benign counterparts (2.69 versus 1.7 cm, P < 0.001). Interestingly, 18% of malignant tumors were smaller than 1 cm in diameter, providing compelling evidence that the size of the tumor should be reconsidered during the assessment of the TNM-WHO clinical staging. The application of the logistic regression and the machine learning model identified the age and the tumor's size as the best predictors with an overall diagnostic accuracy of 0.63, suggesting that these risk factors are sufficient but not exhaustive indicators of the malignancy of CMTs. This multicenter study increases the general knowledge of the main epidemiologica-clinical risk factors involved in the onset of CMTs and paves the way for further investigations of these factors in association with CMTs and in the application of machine learning technology.

DNA methylation landscape of triple-negative ductal carcinoma in situ (DCIS) progressing to the invasive stage in canine breast cancer

Triple-negative breast cancer (TNBC) is a subtype of breast cancer unresponsive to traditional receptor-targeted treatments, leading to a disproportionate number of deaths. Invasive breast cancer is believed to evolve from non-invasive ductal carcinoma in situ (DCIS). Detection of triple-negative DCIS (TN-DCIS) is challenging, therefore strategies to study molecular events governing progression of pre-invasive TN-DCIS to invasive TNBC are needed. Here, we study a canine TN-DCIS progression and investigate the DNA methylation landscape of normal breast tissue, atypical ductal hyperplasia (ADH), DCIS and invasive breast cancer. We report hypo- and hypermethylation of genes within functional categories related to cancer such as transcriptional regulation, apoptosis, signal transduction, and cell migration. DNA methylation changes associated with cancer-related genes become more pronounced at invasive breast cancer stage. Importantly, we identify invasive-only and DCIS-specific DNA methylation alterations that could potentially determine which lesions progress to invasive cancer and which could remain as pre-invasive DCIS. Changes in DNA methylation during TN-DCIS progression in this canine model correspond with gene expression patterns in human breast tissues. This study provides evidence for utilizing methylation status of gene candidates to define late-stage (DCIS and invasive), invasive stage only or DCIS stage only of TN-DCIS progression.

Ductal Carcinoma In Situ Progression in Dog Model of Breast Cancer

The mechanisms that drive ductal carcinoma in situ (DCIS) progression to invasive cancer are not clear. Studying DCIS progression in humans is challenging and not ethical, thus necessitating the characterization of an animal model that faithfully resembles human disease. We have characterized a canine model of spontaneous mammary DCIS and invasive cancer that shares histologic, molecular, and diagnostic imaging characteristics with DCIS and invasive cancer in women. The purpose of the study was to identify markers and altered signaling pathways that lead to invasive cancer and shed light on early molecular events in breast cancer progression and development. Transcriptomic studies along the continuum of cancer progression in the mammary gland from healthy, through atypical ductal hyperplasia (ADH), DCIS, and invasive carcinoma were performed using the canine model. Gene expression profiles of preinvasive DCIS lesions closely resemble those of invasive carcinoma. However, certain genes, such as SFRP2, FZD2, STK31, and LALBA, were over-expressed in DCIS compared to invasive cancer. The over-representation of myoepithelial markers, epithelial-mesenchymal transition (EMT), canonical Wnt signaling components, and other pathways induced by Wnt family members distinguishes DCIS from invasive. The information gained may help in stratifying DCIS as well as identify actionable targets for primary and tertiary prevention or targeted therapy.

Caracterización de la expresión de galectina-3 mediante inmunohistoquímica en lesiones intraepiteliales de glándula mamaria de perras sin evidencia de tumor

Las lesiones intraepiteliales (LIEs) son anormalidades morfológicas locales de los ductosy los lobulillos de la glándula mamaria que incrementan el riesgo de cáncer. Los programasde detección temprana de cáncer de seno han incrementado la identificaciónde LIEs. En este sentido, en perras se ha propuesto las LIEs como modelo comparativocon humanos. La galectina-3 está involucrada con la progresión del cáncer en mujeresy hembras caninas pero su papel en el comportamiento biológico de las neoplasias escontradictorio según la célula de origen. El objetivo de este trabajo fue caracterizar laexpresión de la galectina-3 por medio de inmunohistoquímica en 19 glándulas mamarias(GM) de seis perras sin evidencia de tumor que contenían 50 tipos de LIEs y 7 carcinomasinvasivos, teniendo en cuenta el porcentaje de células positivas y la intensidaddel color de la inmunoreacción. No hubo inmunomarcación para galectina-3 en lasadenosis, las hiperplasias ductales usuales, la hiperplasia lobular atípica, las lesiones decélulas columnares, los carcinomas complejos o las hiperplasias complejas. Un papiloma/adenoma con hiperplasia de acinos tuvo inmunomarcación multifocal en 11–50% delas células con moderada intensidad. Dos carcinomas in situ del subtipo lobular (unode grado histológico nuclear intermedio y el otro de alto grado) tuvieron marcación en10% de las células, pero uno tuvo intensidad baja y el otro, intensidad moderada. Loshallazgos sugieren que el papel de la galectina-3 es poco importante en la iniciación delas LIEs, pero sugieren que es una proteína de interés en la progresión de estas lesionesque posiblemente interactúa en el comportamiento biológico de esta enfermedad.

B-mode and contrast-enhanced ultrasonography of the mammary gland during the estrous cycle of dogs

Pathology of the mammary gland is a common health issue in dogs and includes neoplasia, cysts, inflammation and infection. The use of the B-mode (US) and contrast-enhanced (CEUS) ultrasonography may aid in the diagnosis. Previous studies are currently lacking of the ultrasonic images of the mammary gland of healthy bitches in different stages of the estrous cycle and associated normal blood perfusion patterns. The purpose, therefore, was to describe the normal B-mode US and CEUS images of the mammary gland and inguinal lymph node, in six intact female beagles during five different stages of the estrous cycle (proestrus, estrus, early and late diestrus and anestrus). Within the same stage of the estrous cycle, the size (thickness) of the caudal mammary glands increased. During early and late diestrus, all mammary glands increased in thickness and had an increased heterogeneous B-mode ultrasonic appearance. The mammary glands had a heterogeneous, disorganized perfusion pattern when assessed using CEUS. For the cranial abdominal mammary gland, the area under the curve and the mean transit time increased between estrus and late diestrus and decreased between late diestrus and anestrus. For the inguinal mammary gland, only the time to peak was longer during the periods of anestrus compared to estrus whereas all the other contrast parameters did not change during the estrous cycle. In conclusion, hormonal influences cause major changes in the size, appearance and blood perfusion of mammary glands during the estrous cycle and should be considered when evaluating pathological changes of mammary glands.

A first immunohistochemistry study of transketolase and transketolase-like 1 expression in canine hyperplastic and neoplastic mammary lesions

Background

Canine mammary tumors represent the most common neoplasm in female dogs, and the discovery of cancer biomarkers and their translation to clinical relevant assays is a key requirement in the war on cancer. Since the description of the ‘Warburg effect’, the reprogramming of metabolic pathways is considered a hallmark of pathological changes in cancer cells. In this study, we investigate the expression of two cancer-related metabolic enzymes, transketolase (TKT) and transketolase-like 1 (TKTL1), involved in the pentose phosphate pathway (PPP), an alternative metabolic pathway for glucose breakdown that could promote cancer by providing the precursors and energy required for rapidly growing cells.

Results

TKT and TKTL1 protein expression was investigated by immunohistochemistry in canine normal (N = 6) and hyperplastic glands (N = 3), as well as in benign (N = 11) and malignant mammary tumors (N = 17). TKT expression was higher in hyperplastic lesions and in both benign and malignant tumors compared to the normal mammary gland, while TKTL1 levels were remarkably higher in hyperplastic lesions, simple adenomas and simple carcinomas than in the normal mammary glands (P < 0.05).

Conclusions

This study reveals that the expression of a key PPP enzyme varies along the evolution of canine mammary neoplastic lesions, and supports a role of metabolic changes in the development of canine mammary tumors.

Electronic supplementary material

The online version of this article (doi:10.1186/s12917-017-0961-3) contains supplementary material, which is available to authorized users.

Investigation of HER2 expression in canine mammary tumors by antibody-based, transcriptomic and mass spectrometry analysis: is the dog a suitable animal model for human breast cancer?

Canine mammary tumors (CMTs) share many features with human breast cancer (HBC), specifically concerning cancer-related pathways. Although the human epidermal growth factor receptor 2 (HER2) plays a significant role as a therapeutic and prognostic biomarker in HBC, its relevance in the pathogenesis and prognosis of CMT is still controversial. The aim of this study was to investigate HER2 expression in canine mammary hyperplasic and neoplastic tissues as well as to evaluate the specificity of the most commonly used polyclonal anti HER2 antibody by multiple molecular approaches. HER2 protein and RNA expression were determined by immunohistochemistry (IHC) and by quantitative real-time (qRT) PCR. A strong cell membrane associated with non-specific cytoplasmic staining was observed in 22% of carcinomas by IHC. Adenomas and carcinomas exhibited a significantly higher HER2 mRNA expression when compared to normal mammary glands, although no significant difference between benign and malignant tumors was noticed by qRT-PCR. The IHC results suggest a lack of specificity of the FDA-approved antibody in CMT samples as further demonstrated by Western immunoblotting (WB) and reverse phase protein arrays (RPPA). Furthemore, HER2 was not detected by mass spectrometry (MS) in a protein-expressing carcinoma at the IHC investigation. This study highlights that caution needs to be used when trying to translate from human to veterinary medicine information concerning cancer-related biomarkers and pathways. Further investigations are necessary to carefully assess the diagnostic and biological role specifically exerted by HER2 in CMTs and the use of canine mammary tumors as a model of HER2 over-expressing breast cancer.

Canine mammary tumors: a review and consensus of standard guidelines on epithelial and myoepithelial phenotype markers, HER2, and hormone receptor assessment using immunohistochemistry

Although there have been several studies on the use of immunohistochemical biomarkers of canine mammary tumors (CMTs), the results are difficult to compare. This article provides guidelines on the most useful immunohistochemical markers to standardize their use and understand how outcomes are measured, thus ensuring reproducibility of results. We have reviewed the biomarkers of canine mammary epithelial and myoepithelial cells and identified those biomarkers that are most useful and those biomarkers for invasion and lymph node micrometastatic disease. A 10% threshold for positive reaction for most of these markers is recommended. Guidelines on immunolabeling for HER2, estrogen receptors (ERs), and progesterone receptors (PRs) are provided along with the specific recommendations for interpretation of the results for each of these biomarkers in CMTs. Only 3+ HER2-positive tumors should be considered positive, as found in human breast cancer. The lack of any known response to adjuvant endocrine therapy of ER- and PR-positive CMTs prevents the use of the biological positive/negative threshold used in human breast cancer. Immunohistochemistry results of ER and PR in CMTs should be reported as the sum of the percentage of positive cells and the intensity of immunolabeling (Allred score). Incorporation of these recommendations in future studies, either prospective or retrospective, will provide a mechanism for the direct comparison of studies and will help to determine whether these biomarkers have prognostic significance. Finally, these biomarkers may ascertain the most appropriate treatment(s) for canine malignant mammary neoplasms.

Morphological aspects and immunophenotypic profiles of mammary carcinomas in benign-mixed tumors of female dogs

Carcinoma in benign-mixed tumor (CBMT) is common in the female canine mammary gland and comprises malignant epithelial between benign mesenchymal elements. This study investigated the morphological aspects of 29 CBMT and their immunophenotypical profiles, by using an immunohistochemistry panel based on five molecular markers—estrogen receptor (ER), progesterone receptor (PR), human epidermal growth factor receptor 2 (HER2), cytokeratin 5 (CK5), and human epidermal growth factor receptor 1 (EGFR). From these, CBMT was classified into four subtypes: luminal A, luminal B, HER2-like, basal-like, and normal. “In situ” and invasive carcinomatous components were analyzed and compared. Histological grade I carcinoma was observed in 16 cases (55.2%) of the tumors analyzed, grade II in 10 cases (34.5%), and grade III in three cases (10.3%). The invasive carcinomatous component has shown, more frequently, luminal A (12/29 cases, 41.4%), followed by basal-like phenotype (8/29 cases, 27.6%). There was high concordance between immunophenotypical profiles of the in situ and invasive carcinomatous components (kappa coefficient = 0.816, P < 0.001). We concluded that CBMT predominantly has features of low-grade neoplasms of malignancy. The various immunophenotypic profiles suggest the origin of these lesions in more than one cell type (luminal and myoepithelial).

Overexpression of α-enolase correlates with poor survival in canine mammary carcinoma

Background

α-Enolase (ENO1) is a key glycolytic enzyme implicated in the development of many human cancers including breast cancer. Increased expression of ENO1 has recently been reported in estrogen (ER)-positive human breast cancer patients. The present study examined the expression of ENO1 and assessed its significance in canine mammary carcinoma.

Results

Immunohistochemical staining was employed to investigate the expression of ENO1 in 82 cases of canine mammary tumor (32 benign tumors and 50 carcinomas). Quantification of immunohistochemistry was carried out using Quick score and the results showed cytoplasmic ENO1 overexpression in 9 of the 50 carcinomas (18%). Overexpression of ENO1 correlated significantly with shorter cause-specific survival (P = 0.019), but was not associated with ER positivity in canine mammary carcinoma.

Conclusions

Our findings suggest that overexpression of ENO1 may be used as a prognostic marker for poor outcome in canine mammary carcinoma.

Elevated Krüppel-like factor 4 transcription factor in canine mammary carcinoma

Background

Krüppel-like factors (KLFs) are critical regulators of biological and physiological systems and have been extensively studied for their roles in cell proliferation, differentiation and survival in the context of cancer. Among the KLFs, KLF4 is highly expressed in human breast cancers and plays an oncogenic role. The present study examined the expression of KLF4 and assessed its significance in canine mammary carcinoma.

Results

Immunohistochemistry was employed to investigate the expression of KLF4 in 142 cases of canine mammary tumor. 75 of the 142 (52.8%) cases were histologically confirmed as mammary carcinoma. Quantification of immunohistochemistry was carried out using Quick score which multiply the staining intensity by the percentage of positive cells. High KLF4 expression was identified in 44 of the 75 (59%) dogs with mammary carcinoma and none in the benign cases. High KLF4 expression occurred only in the tumor cells and not the adjacent normal cells in mammary carcinoma (P < 0.001). Moreover, the high expression level of KLF4 expression was statistically associated with poor grade, late stage, histological subtypes of simple and complex carcinoma, and shorter 24-month survival. The Kaplan-Meier survival analysis also indicated that dogs with high nuclear KLF4 expression had a significantly shorter survival than those with low/moderate KLF4 expression (P = 0.011).

Conclusions

KLF4 is highly and frequently expressed in canine mammary carcinoma and correlates with a more aggressive phenotype.

Mammography and ultrasound imaging of preinvasive and invasive canine spontaneous mammary cancer and their similarities to human breast cancer

Understanding the evolution of proliferative breast disease such as atypical hyperplasia and carcinoma in situ is essential for clinical management of women diagnosed with these lesions. Therefore, an animal model that faithfully represents human breast disease in every aspect from spontaneity of dysplasia onset, histopathologic features, and genetics to clinical outcome is needed. Previously, we studied canine spontaneous atypical hyperplasia and ductal carcinoma in situ (low, intermediate, and high grade) and reported their similarities to human lesions in histopathologic and molecular features as well as prevalence. To further validate the resemblance of these lesions to humans, we examined their mammographic and sonographic characteristics in comparison with those of human's as well as the potential of the human Breast Imaging Reporting and Data System (BI-RADS) to predict canine disease. Nonlesional, benign, and malignant mammary glands of dogs presented to Sassari Veterinary Hospital were imaged using mammography and ultrasonography. The images where then analyzed and statistically correlated with histopathologic findings and to their similarities to humans. Our results showed that canine mammary preinvasive lesions, benign, and malignant tumors have mammographic abnormalities, including the presence, pattern, and distribution of macrocalcification and microcalcification, similar to their human counterparts. BI-RADS categorization is an accurate predictor of mammary malignancy in canine, with 90% sensitivity and 82.8% specificity. The similarities of mammographic images and the ability of BI-RADS to predict canine mammary malignances with high specificity and sensitivity further confirm and strengthen the value of dog as a model to study human breast premalignancies for the development of prognostic biomarkers.

Classification and grading of canine mammary tumors

Mammary neoplasms are the most common neoplasm in female dogs. Two histologic classification systems for canine mammary tumors and dysplasias have been published: the first in 1974 and a modification in 1999. This article provides a brief overview of the two histologic classification systems. Since the publication of the second system, several new histologic subtypes of canine mammary neoplasms have been described. These have been incorporated into the proposed new classification system. This article also compares the grading systems for canine mammary carcinomas and their use for prognosis, along with the histologic classification.

Canine mammary tumours, an overview

Canine mammary tumours (CMTs) are the most common neoplasms in intact female dogs. Although the prevalence of these tumours decreases in regions where preventive ovari(ohyster)ectomy is performed, it remains an important disease entity in veterinary medicine. Moreover, treatment options are limited in comparison with human breast cancer. Nevertheless, recent human treatment protocols might have potential in bitches suffering from CMTs.

Histological and Immunohistochemical Identification of Atypical Ductal Mammary Hyperplasia as a Preneoplastic Marker in Dogs

This study describes and evaluates the morphological and molecular relationship between canine mammary ductal hyperplasias with atypia and canine mammary neoplasias. Ductal hyperplasia was identified in association with malignant neoplasia in 56 of the 115 cases (48,8%), and although ductal hyperplasia without atypia was the type most frequently noted in the cases, most examples of hyperplasia with atypia were associated with mammary tumors. Estrogen receptor, E-cadherin, and cytokeratins 1, 5, 10 and 14 (CK34bE12) expression was quite lower than in normal mammary tissue, and HER2 overexpression was absent in all proliferative cells of ductal hyperplasia. The Ki-67 expression, epidermal growth factor receptor and progesterone receptor expression appeared higher in those hyperplastic lesions analyzed than in normal mammary glands. These findings suggest that canine mammary atypical hyperplasia may play an important role in the process of malignant neoplastic transformation, with molecular alterations that are similar to precursor lesions reported in humans.