The Expression of p63 and Cytokeratin 5 in Mixed Tumors of the Canine Mammary Gland Provides New Insights into the Histogenesis of These Neoplasms

Canine mammary carcinoma: current therapeutic targets and future perspectives – a review

Canine mammary carcinoma (CMC) is the most common neoplasm in bitches, and it shares many biological similarities with breast cancer in humans. Drug resistance, high epigenetic mutations, and relapse rates are among the challenges which eventually urge the need for a veterinary oncologist to discover new therapeutic approaches that are more effective and safer. Therefore, in this review, we also cover the current therapeutic strategies from human medicine for the future perspectives of tumor immunotherapy in veterinary medicine. These strategies have great potential to be employed as therapeutic or prophylactic options due to their ability to modulate a specific and potent immune response against CMC. As we acquire a better understanding of canine tumor immunology, we can move towards a brighter prognosis. Additionally, we report on the recent successful studies in breast cancer that may benefit canines as well.

Establishment of a direct 2.5D organoid culture model using companion animal cancer tissues

Like humans, cancer affects companion animals with similar genetic risks and incident rates. To improve treatment strategies for pet cancers, new research models are necessary. Patient-derived 3D organoid culture models are valuable and ensure the development of new effective therapies. In the previous study, we established a 3D organoid-derived 2.5D organoid culture model that recapitulated some characteristics of their parental 3D organoids. In the present study, we aimed to generate a 2.5D organoid culture model directly from cancer-diseased dogs and cats using special 2.5D media. The primary cultured cells in 2.5D media (direct 2.5D organoids) showed better attachment, growth, marker expression, and faster proliferation speed than those cultured in normal Dulbecco's Modified Eagle Medium media. The direct 2.5D organoids showed expression of each specific marker to their original cancer tissues and exhibited tumorigenesis in vivo. Moreover, the direct 2.5D organoids exhibited concentration-dependent responses to anti-cancer drugs, and different sensitivity profiles were shown among the strains. Our data suggest that the direct 2.5D organoid culture model might become a useful tool beyond 2D cell lines to study cancer biology in companion animals and could provide new platforms for screening the anti-cancer drugs.

Pathological Features and Molecular Phenotype of MMTV Like-Positive Feline Mammary Carcinomas

Simple Summary

Mouse mammary tumour virus-like (MMTV-like) is suspected to be involved in human breast cancer and feline mammary carcinomas (FMCs). We previously reported the identification of MMTV-like sequences and viral protein in six of 78 FMCs collected in Tuscany, Italy. To corroborate this finding, FMCs samples collected from a different geographic area were investigated. MMTV-like sequences and p14 protein were identified in three of 24 FMCs collected at the University of Bologna, one tubular carcinoma, one tubulopapillary carcinoma and one ductal carcinoma. All the examined FMCs from Pisa and Bologna were submitted to immunohistochemistry for molecular phenotype characterization. Of the nine positive FMCs, six were basal-like and three luminal-like. This study highlights the presence of MMTV-like sequences and protein in FMCs of different geographic areas. The characterization of molecular phenotype could contribute to understand the possible role of MMTV-like virus in FMC biological behaviour.

Abstract

In the last few years MMTV-like nucleotide sequences were detected in some feline and canine mammary tumours. Due to the confirmed role of cats in the epidemiology of the MMTV-like virus, the aim of this study was to investigate the main pathological features of positive feline mammary carcinomas (FMCs). Twenty-four FMCs were collected at the University of Bologna, submitted to laser microdissection and analysed by nested fluorescence-PCR using primer sets specific for MMTV env sequence. For immunohistochemistry, an antibody against MMTV protein 14 (p14) was used. MMTV-like sequences were detected in three out of 24 FMCs (12.5%), one tubular carcinoma, one tubulopapillary carcinoma and one ductal carcinoma. All PCR-positive tumours were also positive for p14. Multiple nucleotide alignment has shown similarity to MMTV ranging from 98% to 100%. All the 102 examined FMCs were submitted to immunohistochemistry for molecular phenotyping. Of the nine MMTV-like positive FMCs, six were basal-like and three luminal-like. Our results demonstrate MMTV-like sequences and protein in FMCs of different geographic areas. Molecular phenotyping could contribute to understand the possible role of MMTV-like virus in FMC tumor biology.

Vitamin D receptor (VDR) expression in different molecular subtypes of canine mammary carcinoma

BACKGROUND

The molecular-based classification of canine mammary carcinomas (CMCs) has been the focus of much current research. Both in canines and humans, the triple-negative (TN) molecular subtype of mammary cancer is defined by a lack of expression of progesterone receptor (PR), oestrogen receptor (ER) and HER2. It has a poor prognosis; no effective targeted therapy is available. Vitamin D displays anticarcinogenic properties, and the expression of its receptor (VDR) has been found in different molecular subtypes, being about 30-40 % of TN breast cancer (TNBC) positive to it. We assessed the VDR expression in the different molecular subtypes of 58 CMCs from 45 female dogs using an immunohistochemical panel for the molecular classification of included: PR, ER, HER2, cytokeratin (CK) 5, CK14, and Ki67. In addition, we studied the relationship among the molecular subtypes of CMCs and clinicopathologic parameters.

RESULTS

Investigation showed VDR positivity in 45.0 % of the triple-negative CMCs (TNCMCs), 27.3 % of luminal B and 19.0 % of luminal A. Luminal A was the most molecular subtype represented of the total tumours (36.2 %), followed of TNCMCs (34.5 %), luminal B (20.7 %) and HER2-overexpression (10.3 %). Both HER2-overexpression and TNCMC subtypes were positively related to lymphatic invasion (P = 0.028), simple histologic subtype (P = 0.007), a higher histological grade (P = 0.045) and a trend to higher proliferation index (P = 0.09).

CONCLUSIONS

The highest VDR expression was observed in TNCMC, being almost half of them (45 %) positive to this receptor. VDR expression was absent in HER2-overexpression tumours and low in luminal A and B molecular subtypes.

A Comparative Review of Mixed Mammary Tumors in Mammals

Mixed tumors are characterized by the histological identification of two or more cell types. Commonly, a mixture of epithelial and myoepithelial cells is included in abundant stroma, which can consist of myxoid, chondroid or bony matrices. Spontaneously arising mixed tumors are rare lesions in the human breast but are common in human salivary glands and canine mammary glands. Subtle histopathological characteristics and overlapping attributes of malignant lesions with other benign lesions can lead to a diagnostic challenge. Mixed tumors can present as benign or malignant. While malignant mixed tumors are quite rare in the human breast they have a poor prognosis. Benign mixed mammary tumors occur more frequently in female dogs than in humans and are usually associated with a good prognosis. This review will provide a comprehensive overview of mixed mammary tumors, across various mammalian species.

Immunohistochemical expression of p63 protein and calponin in canine mammary tumours

The aim of this study was to compare the expression of p63 protein and calponin in terms of their affinity and specificity for myoepithelial cells in canine mammary tumours. The studied material included 10 benign and 32 malignant mammary tumours from female dogs treated with mastectomy. Primary mouse monoclonal antibodies directed against p63 protein clone 4A4 and calponin clone CALP were used in single- and doublestain system of immunohistochemical reaction. The investigations have shown that majority of myoepithelial cells in benign tumours and carcinomas in situ exhibited strong positive labelling for both markers. In other malignant tumours strong immunoreactivity was observed in resting myoepithelial cells (MECs) and hypertrophic myoepithelial cells (HMECs), while the immunoreactivity in spindle-stellate myoepithelial cells (SMECs) and rounded myoepithelial cells (RMECs) was moderate. The granular-diffuse nuclear expression of p63 protein was observed only in myoepithelial cells. In terms of calponin, diffuse cytoplasmic expression was noted not only in myoepithelial cell but also in some stromal fibroblasts and vascular smooth muscle cells. The epithelial cells did not exhibit specific expression of the investigated markers. The obtained results indicate that p63 is a sensitive and more specific marker of myoepithelial cells in canine mammary tumours compared with calponin. These findings suggest that the immunohistochemical analysis peformed with the use of p63 can be a valuable complement of routine histological examinations of canine mammary tumours facilitating identification of tumours with myoepithelial component.

Analysis of Contractility and Invasion Potential of Two Canine Mammary Tumor Cell Lines

Cancer cells are surrounded by a mechanically and biochemically distinct microenvironment that undergoes dynamic changes throughout the neoplastic progression. During this progression, some cancer cells acquire abnormal characteristics that potentiate their escape from the primary tumor site, to establish secondary tumors in distant organs. Recent studies with several human cancer cell lines have shown that the altered physical properties of tumor cells, such as their ability to apply high traction forces to the surroundings, are directly linked with their potential to invade and metastasize. To test the hypothetical interconnection between actomyosin-mediated traction forces and invasion potential within 3D-microenvironment, we utilized two canine mammary tumor cell lines with different contractile properties. These cell lines, canine mammary tumor (CMT)-U27 and CMT-U309, were found to have distinct expression patterns of lineage-specific markers and organization of actin-based structures. In particular, CMT-U309 carcinoma cells were typified by thick contractile actomyosin bundles that exerted high forces to their environment, as measured by traction force microscopy. These high contractile forces also correlated with the prominent invasiveness of the CMT-U309 cell line. Furthermore, we found high contractility and 3D-invasion potential to be dependent on the activity of 5′AMP-activated protein kinase (AMPK), as blocking AMPK signaling was found to reverse both of these features. Taken together, our findings implicate that actomyosin forces correlate with the invasion potential of the studied cell lines.

Myoepithelial cells in canine mammary tumours

Mammary tumours are the most common neoplasms of female dogs. Compared to mammary tumours of humans and cats, myoepithelial (ME) cell involvement is common in canine mammary tumours (CMT) of any subtype. Since ME cell involvement in CMT influences both histogenetic tumour classification and prognosis, correct identification of ME cells is important. This review describes immunohistochemical methods for identification of canine mammary ME cells used in vivo. In addition, phenotypic and genotypic methods to isolate ME cells for in vitro studies to analyse tumour-suppressor protein production and gene expression are discussed. The contribution of ME cells to both histogenetic classifications and the prognosis of CMT is compared with other species and the potential use of ME cells as a method to identify carcinoma in situ is discussed.

p63 and E-cadherin Expression in Canine Oral Squamous Cell Carcinoma

The expression of p63 and E-cadherin was studied in 22 oral squamous cell carcinomas in the dog according to immunohistochemical techniques. The association between these markers and clinicopathologic parameters was assessed. All tumor cells studied showed enhanced p63 expression. Regarding E-cadherin expression, 17 of 22 cases (77.3%) showed decreased immunoreactivity, and in 13 of 22 cases (59.1%), its expression was cytoplasmic. Neither p63 nor E-cadherin expression patterns were associated with tumor size, bone invasion, or lymph node metastasis. p63 score was related to proliferating cell nuclear antigen proliferative index (P = .020). A statistically significant correlation between the expression patterns of these 2 markers was noted (P = .026). Furthermore, they were related with tumor grade. An atypical p63 labeling and a cytoplasmic E-cadherin staining were statistically related with a higher tumor grade (P = .022 and P = .017, respectively). These findings suggest that changes in p63 and E-cadherin expression are frequent events in oral squamous cell carcinoma in dogs.

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.

Isolation, purification, culture and characterisation of myoepithelial cells from normal and neoplastic canine mammary glands using a magnetic-activated cell sorting separation system

Mammary gland tumours, the most common malignant neoplasm in bitches, often display myoepithelial (ME) cell proliferation. The aim of this study was to isolate, purify, culture and characterise ME cells from normal and neoplastic canine mammary glands. Monodispersed cells from three normal canine mammary glands and five canine mammary tumours were incubated with an anti-Thy1 antibody and isolated by magnetic-activated cell sorting (MACS). Cells isolated from two normal glands (cell lines CmME-N1 and CmME-N2) and four tumours (cell lines CmME-K1 from a complex carcinoma, CmME-K2 from a simple tubulopapillary carcinoma, and CmME-K3 and CmME-K4 from two carcinomas within benign tumours) were cultured in supplemented DMEM/F12 media for 40days. Cell purity was >90%. Tumour-derived ME cell lines exhibited heterogeneous morphology, growth patterns and immunocytochemical expression of cytokeratins, whereas cell lines from normal glands retained their morphology and levels of cytokeratin expression during culture. Cell lines from normal glands and carcinomas within benign tumours grew more slowly than those from simple and complex carcinomas. This methodology has the potential to be used for in vitro analysis of the role of ME cells in the growth and progression of canine mammary tumours.

Molecular portrait-based correlation between primary canine mammary tumor and its lymph node metastasis: possible prognostic-predictive models and/or stronghold for specific treatments?

Background

This study aimed to evaluate the relationship between the molecular phenotype of the primary mammary tumor and its related lymph node metastasis in the dog to develop prognostic-predictive models and targeted therapeutic options.

Results

Twenty mammary tumor samples and their lymph node metastases were selected and stained by immunohistochemistry with anti-estrogen receptor (ER), -progesterone receptor (PR), -human epidermal growth factor receptor 2 (c-erbB-2), -cytokeratin 5/6 (CK 5/6), -cytokeratin 14 (CK14), -cytokeratin 19 (CK 19) and -protein 63 (p63) antibodies. Four phenotypes (luminal A, luminal B, c-erbB2 overexpressing and basal-like) were diagnosed in primary tumors and five (luminal A, luminal B, c-erbB-2 overexpressing, basal-like and normal-like) in the lymph node metastases. Phenotypic concordance was found in 13 of the 20 cases (65%), and seven cases (35%) showed discordance with different lymph node phenotypic profile from the primary tumor.

Conclusions

The phenotype of the primary tumor assumes a predictive-therapeutic role only in concordant cases, meaning that both the primary tumor and its lymph node metastasis should be evaluated at the same time. A treatment plan based only on the primary tumor phenotype could lead to therapeutic failures if the phenotype of the lymph node metastasis differs from that of the primary tumor.

Canine mammary mixed tumours: a review

Mammary mixed tumours are the most frequent neoplasias in female dogs. In humans, mixed tumours are frequently found in the salivary glands and are known as pleomorphic adenomas. In addition to their histomorphologic similarities, mixed tumours and pleomorphic adenomas have the potential to become malignant and give rise to carcinomas in mixed tumours and carcinomas ex-pleomorphic adenoma, respectively. The factors associated with malignant transformation are still poorly known in the case of canine mixed tumours. However, this form of neoplasia tends to be associated with a better prognosis than other malignant histological types. This paper discusses the main features associated with female canine mammary mixed tumours.

P-cadherin expression in feline mammary tissues

The search for molecular markers in the feline mammary gland, namely, the adhesion molecules belonging to the cadherin family, is useful in the understanding of the development of mammary carcinomas in felines and humans. To study P-cadherin expression in the feline mammary gland, 61 samples of normal (n = 4), hyperplastic (n = 12), and neoplastic (n = 45) feline mammary tissues were examined. In both normal and hyperplastic mammary tissues as well as in benign tumours, P-cadherin immunolabelling was restricted to myoepithelial cells. In malignant tumours, however, there was an aberrant epithelial P-cadherin immunoexpression in 64.1% (n = 25) of cases, with a membranous and/or cytoplasmic pattern of distribution. A statistically significant relationship was seen between epithelial P-cadherin expression and malignant mammary lesions (P = 0.0001). In malignant mammary tumours, there was likewise a statistically significant relationship between aberrant P-cadherin immunoexpression and histological grade (P = 0.0132). Aberrant epithelial P-cadherin expression seems to be related to malignancy in the feline mammary gland. To confirm the results of this investigation, further studies with larger samples and follow-up studies are warranted.

Morphology of the myoepithelial cell: immunohistochemical characterization from resting to motile phase

Myoepithelium is present in canine mammary tumors as resting and proliferative suprabasal and spindle and stellate interstitial cells. The aim of this paper was to evaluate a panel of markers for the identification of four different myoepithelial cell morphological types in the normal and neoplastic mammary gland and to investigate immunohistochemical changes from an epithelial to a mesenchymal phenotype. Cytokeratin 19 (CK19), cytokeratin 5/6 (CK5/6), cytokeratin 14 (CK14), estrogen receptor (ER), p63 protein, vimentin (VIM), and α-smooth muscle actin (Alpha-SMA) antibodies were used on 29 neoplasms (3 benign and 3 malignant myoepithelial tumors, 7 carcinomas in benign-mixed tumors and 16 complex carcinomas) and on normal tissue of mammary glands. All these antibodies were also tested on 3 mammary tissues from animals with no mammary pathology. The myoepithelial markers were well expressed in the suprabasal cells and gradually lost in the motile types, with the stellate cells maintaining only VIM expression typical of mesenchyma. ER labeled some resting and motile myoepithelial cells. On the basis of our results, we propose a transition from myoepithelial immotile cells into migratory fibroblast-like cells. This transition and the characterization of an immunohistochemical panel for resting and motile myoepithelial cells shed more light on the biological behavior of myoepithelial cells.

Molecular phenotype in mammary tumours of queens: correlation between primary tumour and lymph node metastasis

The molecular characterization of mammary tumours represents a new stage in the development of effective predictive models and targeted therapies. The aim of this study was to evaluate the relationship between the molecular phenotype of a primary feline mammary tumour and that of a related lymph node metastasis. Twenty-one mammary tumour samples and their lymph node metastases were selected and evaluated immunohistochemically for expression of oestrogen receptor, progesterone receptor, human epidermal growth factor receptor 2 (c-erbB-2), cytokeratin 5/6, cytokeratin 14, cytokeratin 19 and protein 63. Mammary tumours were classified into five subtypes: luminal A, luminal B, c-erbB-2 overexpressing, basal-like and normal-like, based on an algorithm applied in both human and veterinary medicine. Concordance between the primary tumour and its lymph node metastasis was detected in 12 of 21 cases (57.1%). In the remaining nine cases (42.9%) there was discordance in the molecular profile at the two sites. Therefore, the tumour molecular profile must be evaluated in both sites in order to obtain definitive identification of the tumour profile (or profiles) and to plan an appropriate therapy.

Complex apocrine carcinoma with dominant myoepithelial proliferation in a dog

A rare case of complex apocrine carcinoma displaying dominant myoepithelial proliferation developed in the right leg subcutis of a 10-year-old male dog. The major cell population consisted of diffusely proliferating p63-expressing neoplastic cells that were largely myoepithelial in origin co-expressing α-smooth muscle actin. A small portion of the cell population consisted of concomitant basal epithelial cells lacking α-smooth muscle actin expression. The minor population consisted of p63-negative apocrine gland cells that expressed cytokeratin 8. The myoepithelial cell population showed a rather stronger proliferation activity than did the apocrine epithelial population. Thus, this tumor might have been derived from basal epithelial cells characterized by more predominant myoepithelial differentiation than luminal apocrine epithelial differentiation.

Myeloid metaplasia in canine mixed mammary tumors: occurrence and characterization

BACKGROUND

Mixed tumors are among the most frequent mammary neoplasms in female dogs. Some of these tumors present bone marrow associated with the newly formed osseous tissue, characteristic of myeloid metaplasia.

OBJECTIVE

To evaluate the occurrence of these lesions in a series of mixed tumors, and determine its histomorphological characteristics.

ANIMALS AND METHODS

In total, 384 canine mammary mixed tumors from 289 animals have been reviewed. The lesions were classified according to the presence of osseous metaplasia associated with myeloid metaplasia or extramedullary hematopoiesis. Myeloid metaplasia characterization was determined from the morphological characteristics and organization of the cells and adjacent tissues. Cytoplasmic staining for CD31 and Factor VIII were used as a criterion to confirm the presence of blood vessels and megakaryocytes, respectively.

RESULTS

The 384 cases included 206 benign and 178 carcinomas in mixed tumors. Osseous metaplasia was present in 16.1% and calcified areas exclusively in 3.1% lesions. Among all osseous metaplasia, 33.9% presented some type of extramedullary hematopoiesis, of which 71.4% were classified as myeloid metaplasia and 28.6% as extramedullary hematopoiesis. Myeloid metaplasia cases consisted of 67% benign mixed tumors and 33% carcinomas in mixed tumors. CD31 and Factor VIII expression occurred in all myeloid metaplasia, confirming the presence of blood capillaries and megakaryocytes. Myeloid metaplasia was observed in 24% of mixed tumors containing osseous metaplasia and in 4% of all mixed tumors analyzed.

CONCLUSION

Despite the low frequency of this lesion, additional studies are needed to understand the implications of myeloid metaplasia in canine mammary mixed tumors.

Tubulopapillary carcinoma of the mammary gland in a maned wolf (Chrysocyon brachyurus): histopathological and immunophenotypical analysis

A maned female wolf (Chrysocyon brachyurus) showed nodules in the inguinal and left abdominal cranial mammary glands. The mammary gland was surgically excised, and microscopic analysis revealed epithelial cell proliferation in a tubular and papillary pattern; delicate fibrovascular stalks presenting numerous layers of moderately pleomorfic epithelial cells were observed. This histologic appearance was compatible with a diagnosis of mammary tubulopapillary carcinoma. The immunohistochemical profile revealed nuclear positivity for estrogen (70%) and progesterone (at least 90% of the neoplastic cells). The myoepithelium-associated with neoplastic cells lacked integrity, as evidenced by failed smooth muscle alpha actin reactivity in microinvasive areas. A low proliferation index was observed (3.4%). To the authors' knowledge, the present case represents the first finding of female tubulopapillary carcinoma in a mammary gland in this species.

Complex mammary adenoma with sebaceous differentiation in a dog

Sebaceous metaplasia arising within a complex adenoma of the left fourth mammary gland is described in a 9-year-old miniature pinscher bitch. Microscopically, the tumour was composed of tubular and ductular structures admixed with clusters of spindle-shaped, myoepithelial-like cells and units formed of well-differentiated sebocytes surrounded by basaloid cells. Abundant lipid droplets were identified within the latter population by Sudan III staining. Immunohistochemical expression of cytokeratin AE1/AE3 was detected in epithelial cells and in the cells with sebaceous differentiation.

A Retrospective Study of Those Histopathologic Parameters Predictive of Invasion of the Lymphatic System by Canine Mammary Carcinomas

The aim of the present study was to determine which histopathologic parameters of primary canine mammary carcinomas (CMCs) could predict metastatic spread via the lymphatic system. A modification of the World Health Organization classification was applied to 245 CMCs. In addition to tumor subtype, neoplastic infiltration of the surrounding mammary stroma, vasculogenic mimicry, and micropapillary pattern were evaluated, and 2 histologic grading systems were used for each sample. A statistical analysis was undertaken to determine the relationship between these histopathologic parameters and the detection of lymphatic vessels invasion (LVI) and regional lymph node metastases (RLM). To compare the predictive value for lymphatic spread of the 2 histologic grading systems, the Akaike information criterion was measured. The classification into tumor subtypes was significant ( P < .01) in predicting the risk of LVI and RLM. Peripheral infiltration, vasculogenic mimicry, and micropapillary pattern were found in 170 of 245 (69.4%), 32 of 245 (13.1%), and 54 of 245 (22.0%) CMCs. The presence of peripheral infiltration was significantly associated ( P < .001) with both LVI and RLM, and a similar relation ( P < .05) was found for the micropapillary pattern. Vasculogenic mimicry was not predictive of invasion of the lymphatic system. Both histologic grading systems were significant predictors ( P < .001) of the risk of LVI and RLM. The grading system that included a more rigorous evaluation of the neoplastic mitotic activity had the lower Akaike information criterion values, thus indicating a better predictive ability. The study confirms the significant prognostic role for the modified World Health Organization classification of CMCs and the prognostic value of additional histopathologic parameters.

Development, anatomy, histology, lymphatic drainage, clinical features, and cell differentiation markers of canine mammary gland neoplasms

Mammary neoplasms are the most common neoplasm in female dogs. This article describes the embryologic development, normal anatomy, and histology of the canine mammary gland from the onset of first estrous and the changes that occur in the mammary gland during the estrus cycle. The clinical features of canine mammary gland tumors and their relation to prognosis are discussed, including age, hormones, breed, diet, and obesity. Additional clinical prognostic factors including clinical presentation, tumor size, and lymph node status at the time of presentation are discussed in relation to diagnosis and tumor staging. Immunohistochemical evaluation of the cell differentiation markers of the normal and neoplastic canine mammary gland is described and compared with similar studies in humans; the ways these markers may be used to assist with the prognosis of canine mammary neoplasms are discussed.

Immunohistochemical Expression of p63 and ΔNp63 in Mixed Tumors of Canine Mammary Glands and Its Relation with p53 Expression

The immunohistochemical expression of p63, ΔNp63, and p53 was studied in mixed tumors of canine mammary glands (13 benign mixed tumors and 19 carcinomas arising from benign mixed tumors) to determine the role of p63 and its isoform ΔNp63 in the development of mixed tumors, as well as to assess its relation with p53. P63 was expressed in myoepithelial cells of all benign mixed tumors and in 18 of 19 carcinomas in mixed tumors. The p63-negative carcinoma in mixed tumors was invasive, and a loss of p63 was detected in the other malignant tumors showing a discontinuous p63-stained myoepithelial layer. ΔNp63 was expressed in all benign mixed tumors but only in p63-positive carcinomas in mixed tumors. Despite its positive correlation with p63 expression in carcinomas in mixed tumors ( r = 0.8323, P < .00001), ΔNp63 expression showed a decrease in benign tumors. Positivity for p53 was detected in 2 of 13 and 1 of 19 benign mixed tumors and carcinomas in mixed tumors, respectively. There was no correlation between p63 or ΔNp63 and p53 expression. Our data support the notion that the decrease of p63 expression, in particular of its isoform ΔNp63, seems to be an important factor in the development of carcinomas in mixed tumors.

An assessment of the clonality of the components of canine mixed mammary tumours by mitochondrial DNA analysis

The aim of this study was to investigate if mutations in the mitochondrial DNA (mtDNA) D-loop fragment control region of canine mammary mixed tumours could be used as clonal markers that identified the cell population of origin. Ten benign mixed mammary tumours and nine carcinomas arising from benign mixed tumours were microdissected and DNA from epithelial and mesenchymal tumour cells and from normal mammary tissue was examined for sequence variations in a fragment of the hypervariable control region. Identical sequence variants in both the epithelial and mesenchymal components (as well as in the corresponding normal tissue) were found in 80% of the benign mixed tumours and in 89% of the carcinomas arising from benign mixed tumours suggesting a shared clonal origin. The distinctive sequence alterations identified in the epithelial and mesenchymal components of 15.8% of all 19 tumours examined, suggests the possibility that a minority of mammary tumours are polyclonal in origin or that early clonal divergence occurs. Increased mutation within the mtDNA D-loop fragment of mixed tumour components was not observed.

Expression of p63 normal canine skin and primary cutaneous glandular carcinomas

p63, a recently identified homologue of the p53 protein, is expressed consistently in basal cells of several human multilayered epithelia. In this study, expression of p63 was determined in 31 primary cutaneous glandular carcinomas, including sebaceous, perianal (hepatoid) gland, apocrine and ceruminous carcinomas, as well as their adjacent normal skin. Similar to humans, p63 is a reliable marker for basal and myoepithelial cells in canine epidermis, cutaneous appendages and malignant apocrine and ceruminous gland neoplasms. In sebaceous carcinomas, not only basal cells, but also some sebocytes, showed nuclear staining for p63. Most mature epithelial cells in perianal gland carcinomas exhibited strong p63 expression. Based on these findings, basal/myoepithelial cells could be involved in the oncogenesis of these tumours and p63 might be used as a diagnostic marker in these lesions.