Canine mammary mixed tumours: immunohistochemical expressions of EGFR and HER-2

Collagen modifications predictive of lymph node metastasis in dogs with carcinoma in mixed tumours

Introduction

Mixed tumours in the canine mammary gland are the most common histological type in routine diagnosis. In general, these neoplasms have a favourable prognosis that does not evolve into metastatic disease. However, some cases develop into lymph node metastases and are associated with worse patient survival rates.

Methods

Here is a retrospective study of 46 samples of primary mixed tumours of the canine mammary gland: 15 cases of benign mixed tumours (BMT), 16 cases of carcinoma in mixed tumours without lymph node metastasis (CMT), and 15 cases of carcinomas in mixed tumours with lymph node metastasis (CMTM). In addition, we selected 23 cases of normal mammary glands (NMT) for comparison. The samples were collected from biopsies performed during nodulectomy, simple mastectomy, regional mastectomy, or unilateral/bilateral radical mastectomy. We used multiphoton microscopy, second harmonic generation, and two-photon excited fluorescence, to evaluate the characteristics of collagen fibres and cellular components in biopsies stained with haematoxylin and eosin. We performed Ki67, ER, PR, and HER-2 immunostaining to define the immunophenotype and COX-2. We showed that carcinomas that evolved into metastatic disease (CMTM) present shorter and wavier collagen fibres as compared to CMT.

Results and discussion

When compared to NMT and BMT the carcinomas present a smaller area of fibre coverage, a larger area of cellular coverage, and a larger number of individual fibres. Furthermore, we observed a correlation between the strong expression of COX-2 and a high rate of cell proliferation in carcinomas with a smaller area covered by cell fibres and a larger number of individual fibres. These findings highlight the fundamental role of collagen during tumour progression, especially in invasion and metastatic dissemination.

COX-2 expression in mammary invasive micropapillary carcinoma is associated with prognostic factors and acts as a potential therapeutic target in comparative oncology

Pure human and canine mammary invasive micropapillary carcinoma is a rare malignant epithelial tumor accounting for 0.9 to 2% of all invasive mammary carcinomas and present a high rate of lymphatic invasion and metastasis, with unfavorable prognosis. Surgery and chemotherapy are standard treatments for almost all mammary cancer in both species, as well as hormonal and target therapies available for human patients. However, depending on the patient's clinical staging, satisfactory therapeutic results for invasive micropapillary carcinoma are a challenge due to its high capacity of invasion and metastasis. Cyclooxygenase-2 (COX-2) isoform is an important enzyme stimulated by cytokines, growth factors and oncogenes activation to synthetizes prostaglandins in inflammatory process. COX-2 overexpression is associated with angiogenesis and invasion and contributes to cancer development, disease progression, tumor recurrence and regional lymph node metastasis in human and canine mammary carcinomas. This enzyme can be targeted by non-steroidal anti-inflammatory drugs and its inhibition can reduce tumor growth and metastasis in several cancer types. Given the similarity between both species, the present study aims to elucidate the involvement of COX-2 mRNA and protein expression in canine (cIMPC) and human (hIMPC) pure invasive mammary micropapillary carcinoma, with clinicopathological and survival data. Twenty-nine cases of cIMPC and 17 cases of hIMPC were analyzed regarding histologic type, grade, age, tumor size, lymph node condition, extracapsular extension, inflammatory infiltrate and immunophenotype. When available, information on adjuvant treatment, recurrence, metastasis and overall survival were collected. The present study demonstrated COX-2 protein expression in 65.5% of cIMPC and 92.3% of hIMPC, and an association with more advanced histological grades in bitches and higher Ki67 in women. COX-2 mRNA expression was significantly higher in cIMPC than in hIMPC, and its expression was not associated with COX-2 protein expression in both species. COX-2 mRNA expression was associated with negative-ER hIMPC as well as higher Ki67. cIMPC demonstrated proportional early development, more regional metastasis, and a prevalence of negative estrogen receptor, than hIMPC. This is the first time COX-2 expression is associated with negative prognostic factors in both cIMPC and hIMPC, besides the overexpression of COX-2 protein in such unfavorable histological type, which suggests that COX-2 can act as a potential target in IMPC.

Defucosylated Anti-Epidermal Growth Factor Receptor Monoclonal Antibody Exerted Antitumor Activities in Mouse Xenograft Models of Canine Mammary Gland Tumor

The epidermal growth factor receptor (EGFR) contributes to tumor malignancy through gene amplification and/or protein overexpression. In our previous study, we developed an anti-human EGFR (hEGFR) monoclonal antibody, clone EMab-134 (mouse IgG₁, kappa), which specifically detects both hEGFR and dog EGFR (dEGFR). The defucosylated mouse IgG_2a version of EMab-134 (134-mG_2a-f) exhibits antibody-dependent cellular cytotoxicity (ADCC) and complement-dependent cytotoxicity (CDC) in dEGFR-overexpressed Chinese hamster ovary-K1 (CHO/dEGFR) cells and antitumor activities in mouse xenografts of CHO/dEGFR cells. In this study, the reactivity of 134-mG_2a-f against a canine mammary gland tumor cell line (SNP) was examined by flow cytometry and immunocytochemistry. Furthermore, 134-mG_2a-f highly exerted ADCC and CDC for SNP. The administration of 134-mG_2a-f significantly suppressed the SNP xenograft growth. These results suggest that 134-mG_2a-f exerts antitumor effects against dEGFR-expressing canine mammary gland tumors, and could be valuable as part of an antibody treatment regimen for them.

Antitumor Activities in Mouse Xenograft Models of Canine Mammary Gland Tumor by Defucosylated Mouse-Dog Chimeric Anti-Epidermal Growth Factor Receptor Antibody (E134Bf)

The epidermal growth factor receptor (EGFR) contributes to tumor malignancy through gene amplification and/or protein overexpression. In our previous study, we developed an anti-human EGFR (hEGFR) monoclonal antibody (mAb), clone EMab-134 (mouse IgG₁, kappa), which specifically detects both hEGFR and dog EGFR (dEGFR). The defucosylated mouse IgG_2a version of EMab-134 exhibits antibody-dependent cellular cytotoxicity (ADCC) and complement-dependent cytotoxicity (CDC) in dEGFR-overexpressed CHO-K1 (CHO/dEGFR) cells and antitumor activities in mouse xenografts of CHO/dEGFR cells. In this study, we produced a defucosylated mouse-dog chimeric anti-EGFR mAb (E134Bf), and the reactivity of E134Bf against a canine mammary gland tumor cell line (SNP) was examined by flow cytometry. Furthermore, E134Bf highly exerted ADCC and CDC for SNP cells. The administration of E134Bf with canine mononuclear cells significantly suppressed the SNP xenograft growth. These results suggest that E134Bf exerts antitumor effects against dEGFR-expressing canine mammary gland tumors and could be valuable as part of an antibody treatment regimen for them.

Antitumor Activities in Mouse Xenograft Models of Canine Fibroblastic Tumor by Defucosylated Anti-Epidermal Growth Factor Receptor Monoclonal Antibody

The epidermal growth factor receptor (EGFR) is involved in tumor malignancy through gene amplification and/or protein overexpression. An anti-human EGFR (hEGFR) monoclonal antibody (clone EMab-134), which explicitly detects hEGFR and dog EGFR (dEGFR), was previously developed. The defucosylated mouse IgG_2a version of EMab-134 (134-mG_2a-f) exhibits antibody-dependent cellular cytotoxicity (ADCC) and complement-dependent cytotoxicity (CDC) in dEGFR-overexpressed CHO-K1 (CHO/dEGFR) cells and antitumor activities in mouse xenografts of CHO/dEGFR cells. In this study, it was shown that 134-mG_2a-f reacts with a canine fibroblastic tumor cell line (A-72) using flow cytometry and immunocytochemistry. Furthermore, 134-mG_2a-f exerted ADCC and CDC on A-72 cell line. The administration of 134-mG_2a-f significantly inhibited the A-72 xenograft growth. These results suggest that 134-mG_2a-f exerts antitumor effects on dEGFR-expressing canine fibroblastic tumors.

Defucosylated Anti-Epidermal Growth Factor Receptor Monoclonal Antibody 134-mG2a-f Exerts Antitumor Activities in Mouse Xenograft Models of Dog Epidermal Growth Factor Receptor-Overexpressed Cells

The epidermal growth factor receptor (EGFR) is a type I transmembrane protein, which is a member of the human epidermal growth factor receptor (HER) family of receptor tyrosine kinases. EGFR is a crucial mediator of cell growth and differentiation and forms homodimers or heterodimers with other HER family members to activate downstream signaling cascades. We previously established an anti-human EGFR (hEGFR) monoclonal antibody (mAb), clone EMab-134 (mouse IgG₁), by immunizing mice with the ectodomain of hEGFR. In this study, the subclass of EMab-134 was converted from IgG₁ to IgG_2a (134-mG_2a) and further defucosylated (134-mG_2a-f) to facilitate antibody-dependent cellular cytotoxicity (ADCC). Although 134-mG_2a-f was developed against hEGFR, it was shown to cross-react with dog EGFR (dEGFR) using flow cytometry. The dissociation constant (K_D) of 134-mG_2a-f against dEGFR-overexpressed CHO-K1 (CHO/dEGFR) cells was determined by flow cytometry to be 3.3 × 10^-9 M, indicating that 134-mG_2a-f possesses a high binding affinity to dEGFR. Analysis in vitro revealed that 134-mG_2a-f contributed to high levels of ADCC and complement-dependent cytotoxicity (CDC) in experiments targeting CHO/dEGFR cells. Furthermore, the in vivo administration of 134-mG_2a-f significantly inhibited the development of CHO/dEGFR in comparison with the results observed in response to control mouse IgG. Taken together, the findings of this study demonstrate that 134-mG_2a-f could be useful as part of a therapeutic regimen for dEGFR-expressing canine cancers.

Expression of VCAN and its receptors in canine mammary carcinomas with or without myoepithelial proliferation

The proteoglycan versican (VCAN) plays a complex role in cancer. The expression of this molecule has been related to invasion and progression in malignant mixed tumors, such as carcinoma in mixed tumors (CMT) of the canine mammary gland. In addition, its interaction with surface cell receptors EGFR, HER-2 and CD44 in malignant epithelial cells may be responsible for proliferation and cellular motility in early stages of cancer. We comparatively evaluated the expression of this proteoglycan and its receptors in in situ and invasive areas of simple carcinomas (SC) and CMT to investigate similarities and differences between these histological types. Immunohistochemistry was performed with anti-VCAN, anti-CD44, anti-EGFR and anti-HER-2 antibodies in 32 cases of SC or CMT. VCAN was highly expressed in stroma adjacent to invasive areas in SC and CMT. CMTs presented comparatively higher expression of VCAN in stroma adjacent to in situ and in invasive areas than in corresponding areas in SCs. In CMT, EGFR and HER-2 expressions were higher in situ compared to invasive areas. In contrast, increased CD44 and EGFR expression was found in invasive areas in SC compared to CMT. These results indicate that versican expression is similarly associated with invasiveness in SC and CMT, however higher levels were seen in CMT suggesting that the presence of myoepithelial proliferation in this tumor type participates in stromal composition and promoting an increase in the expression of versican.

Mixed tumors of the canine mammary glands: Evaluation of prognostic factors, treatment, and overall survival

Mixed tumors are the most frequent mammary gland neoplasms in bitches; however, studies that thoroughly describe their clinicopathological data, treatment approaches, and the survival of bitches with mixed tumors are scarce. This study evaluated the epidemiological and clinicopathological data, prognostic factors, and therapeutic approaches for bitches with mixed tumors. In all, 162 benign mixed tumors, 682 carcinomas in mixed tumors, and 60 carcinosarcomas were included. Regarding tumor size, T3 lesions were predominantly associated with carcinosarcomas, while T1 and T2 lesions occurred more frequently in benign mixed tumors and in carcinomas in mixed tumors. Based on clinical staging, most bitches with benign mixed tumors presented with stage I tumors; 92% of bitches with carcinomas in mixed tumors presented with stage I-III tumors, while 8% presented with stage IV-V tumors; and 70% of bitches with carcinosarcomas presented with stage I-III tumors, while 30% presented with stage IV-V tumors. Surgery was curative for bitches with benign mixed tumors and for those with stage I-III carcinomas in mixed tumors. Combination therapy in bitches with carcinomas in mixed tumors (IV-V) and carcinosarcomas resulted in a higher overall survival compared with bitches who underwent surgery only. Carcinosarcomas presented higher relapse rates and distant metastases than carcinomas in mixed tumors did.

Functional comparison of the human epidermal growth factor receptor and telomerase reverse transcriptase promoters in canine tumor cells

We previously showed that the promoter region of the human epidermal growth factor receptor (hEGFR) gene elicits high transduction efficiency, with transgene expression restricted to canine breast tumor cells. However, it was unclear whether this promoter induces tumor cell-specific transgene expression in canine urothelial carcinoma cells. Furthermore, compared with studies in human cancer cells, the utility of the telomerase reverse transcriptase (TERT) gene promoter for therapeutic transgene expression in canine cancer cells has not been evaluated thus far. Here, we compared the activity of these promoters in canine mammary tumor and urothelial carcinoma cells. Our results showed that compared with the TERT promoter, the hEGFR promoter was more useful as a tumor-specific promoter to induce efficient transgene expression in canine tumor cells.

HER-2 and EGFR mRNA Expression and Its Relationship with Versican in Malignant Matrix-Producing Tumors of the Canine Mammary Gland

Versican expression promotes tumor growth by destabilizing focal cell contacts, thus impeding cell adhesion and facilitating cell migration. It not only presents or recruits molecules to the cell surface, but also modulates gene expression levels and coordinates complex signal pathways. Previously, we suggested that the interaction between versican and human epidermal growth factor receptors may be directly associated with tumor aggressiveness. Thus, the expression of EGFR and HER-2 in these neoplasms may contribute to a better understanding of the progression mechanisms in malignant mammary tumors. The purpose of this study was to correlate the gene and protein expressions of EGFR and HER2 by RNA In Situ Hybridization (ISH) and immunohistochemistry (IHC), respectively, and their relationship with the versican expression in carcinomas in mixed tumors and carcinosarcomas of the canine mammary gland. The results revealed that EGFR mRNA expression showed a significant difference between in situ and invasive carcinomatous areas in low and high versican expression groups. Identical results were observed in HER-2 mRNA expression. In immunohistochemistry analysis, neoplasms with low versican expression showed greater EGFR immunostaining in the in situ areas than in invasive areas, even as the group presenting high versican expression displayed greater EGFR and HER-2 staining in in situ areas. Significant EGFR and HER-2 mRNA and protein expressions in in situ carcinomatous sites relative to invasive areas suggest that these molecules play a role during the early stages of tumor progression.

Dual targeting of EGFR and ERBB2 pathways produces a synergistic effect on cancer cell proliferation and migration in vitro

Members of the epidermal growth factor receptor (EGFR/ERBB) gene family are frequently dysregulated in a range of human cancers, and therapeutics targeting these proteins are in clinical use. We hypothesized that similar pathways are involved in feline and canine tumours and that the same drugs may be of clinical use in veterinary patients. We investigated EGFR and ERBB2 targeting using a panel of feline and canine cell lines. EGFR and ERBB2 were targeted with siRNAs or tyrosine kinase inhibitors (TKIs) and their effect on cellular proliferation, colony formation and migration was investigated in vitro. Here we report that EGFR and ERBB2 combined siRNA targeting produced synergistic effects in feline and canine cell lines similar to that reported in human cell lines. We conclude that dual EGFR and ERBB2 targeting using TKIs should be further evaluated as a potential new therapeutic strategy in feline head and neck and mammary tumours and canine mammary tumours.

Inner nuclear membrane localization of epidermal growth factor receptor (EGFR) in spontaneous canine model of invasive micropapillary carcinoma of the mammary gland

The epidermal growth factor receptor (EGFR) has been described in the nucleus of primary tumors. Accumulation of EGFR at the nucleus is linked to DNA synthesis and cell proliferation, but the pathological significance of nuclear EGFR is not completely understood. The aim of this study was to investigate the nuclear localization of EGFR in invasive micropapillary carcinoma (IMPC) that is an aggressive neoplasm of canine mammary gland. Confocal immunofluorescence of formalin and paraffin-embedded tissue was used to access the subcellular localization of EGFR. Our results demonstrated that EGFR co-localizes with the inner nuclear envelope marker, Lamin B1 in IMPC. Furthermore, EGFR was not localized within the nucleus or at the inner nuclear envelope membrane in mammary carcinoma in mixed tumor (CMT) that is associated with a better prognosis than other malignant histological types. This finding could be useful as a predictive biomarker of therapeutic response for IMPC.

Quantification of epidermal growth factor receptor (EGFR) in canine mammary tumours by ELISA assay: clinical and prognostic implications

The involvement of epidermal growth factor receptor (EGFR) is well established in human breast cancer, however, in canine mammary tumours (CMT), including inflammatory mammary carcinomas (IMC), still needs to be clarified. Enzyme immune assay techniques were used for EGFR determinations in tumour tissue from 45 bitches with CMT and in normal mammary glands from eight control dogs. Higher tissue EGFR levels were found in CMT compared with controls (P < 0.05). In malignant CMT, tissue EGFR elevated concentrations were statistically significantly associated with tumour relapse and/or distant metastasis during follow-up and with reduced disease-free and overall survival times. The IMC cases had the highest tissue EGFR levels compared with other malignant non-IMC tumours (P < 0.001). The results support the hypothesis that EGFR levels influence prognosis in malignant CMT, suggesting that EGFR may represent a therapeutic target in cases of high histological aggressiveness and especially in cases of metastatic phenotype and poor prognosis.

Prognostic significance of tissue and serum HER2 and MUC1 in canine mammary cancer

The aim of our study was to compare serum levels and protein tissue of human epidermal growth factor receptor-2 proto-oncogene (HER2) and mucin 1 (MUC1) using an antigen-capture enzyme-linked immunosorbent assay and immunohistochemistry (IHC) in canine mammary carcinomas and investigate how the 2 markers correlate with dogs with metastasis and without metastasis to a regional lymph node. Forty-eight female dogs were selected, including 14 with non-metastatic cancer, 14 with lymph node metastasis, and 20 healthy animals. Serum samples were collected from all the animals and tissues from 28 dogs with malignant mammary tumor with or without metastasis for evaluated HER2 and MUC1 expression. Tissue sample were evaluated for MUC1 and HER2 immunoexpression by IHC. The results showed measurable serum levels of MUC1 and HER2 in all groups. While serum MUC1 levels were significantly higher in animals with metastasis than the other 2 groups, no increase was observed in HER2 serum levels. The MUC1 IHC results showed that only membrane immunostaining was significantly different between the groups. Statistically, there was an association between immunostaining and the serum HER2 levels. Our results indicate that serum concentrations of HER2 and the IHC staining pattern for HER2 in primary tumor do not correlate with the presence of regional metastasis. However, increased concentrations of MUC1 in the serum of dogs with mammary cancer are associated with the presence of metastasis to regional lymph nodes. A membrane pattern of IHC staining for MUC1 in the primary tumor suggests that metastases to regional lymph node are present.

Analysis of EGFR and HER-2 expressions in ductal carcinomas in situ in canine mammary glands

Biomolecular evidence has shown that ductal carcinoma in situ(DCIS) may develop into invasive carcinoma of the canine mammary gland, and mutations in proto-oncogenes HER2 and EGFR; two members of the family of epidermal growth factor receptors, may be involved in this process. The purpose of this study was the characterization of the immunohistochemical expression of the EGFR and HER2 proteins in the process of neoplastic transformation, supposedly present in ductal carcinomas in situin canine mammary glands. Fifteen cases of DCIS were evaluated, with a higher expression of HER2 and EGFR being observed in low-grade carcinomas when compared with high-grade neoplasms, and with a high positive statistical correlation in the latter. Results suggest that aggressive tumors tend to lose the expression of EGFR and HER2 simultaneously. The loss of the expression of these markers may be related to the process of neoplastic progression in canine mammary tumors.

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.

Versican expression in canine carcinomas in benign mixed tumours: is there an association with clinical pathological factors, invasion and overall survival?

Background

Components of the extracellular matrix have been studied in an attempt to elucidate the mechanisms involved in the biological behaviour of tumours. The presence of the proteoglycan versican has been strongly associated with cancer development and progression. However, relationship between versican expression and clinical pathological factors and overall survival has not been previously studied in veterinary medicine. Carcinomas in benign mixed tumours (CBMTs) are one of the most common malignant tumours in female canines and can serve as models for studies of tumour progression. The aim of this study was to evaluate the expression of versican in in situ and invasive carcinomatous areas of canine CBMTs and to evaluate possible associations of versican expression with other classic prognostic factors and overall survival.

Results

Clinical staging; histological grade determination; immunohistochemical staining for versican, E-cadherin and Ki-67; and confirmation of invasion areas by staining for p63 and smooth muscle α-actin (α-SMA) were performed on 49 canine cases of CBMT. Tumour invasion was considered when suspicious Haematoxylin-Eosin (HE)-stained areas showed a total loss of α-SMA and p63 immunoreactivity. Versican immunoreactivity was less intense in the areas adjacent to the in situ carcinomatous regions, compared to invasive regions, which showed extensive and strong staining.

Conclusions

Our data reveal that in canine CBMTs, versican expression differs significantly between invasive and in situ areas, suggesting a role for this molecule in tumour progression. Although a direct relationship exists between versican and invasiveness, our results indicate that the isolated evaluation of this proteoglycan does not represent an independent prognostic factor in canine CBMTs.

Histopathological and immunohistochemical assessment of invasive micropapillary mammary carcinoma in dogs: a retrospective study

Invasive micropapillary carcinoma (IMPC) of the mammary gland, despite its rare occurrence in humans and dogs, is an important neoplasm due to its aggressive behaviour. The aim of this study was to evaluate the clinicopathological and immunophenotypical characteristics of IMPC and to determine the overall survival of dogs with this tumour. Of the selected cases, the majority had >3 cm neoplasms (15/19, 78.95%) and lymph node metastases (16/16, 100%), but only two cases (2/9, 22.2%) had distant metastases. The IMPCs were classified as either pure (15/22, 68.18%) or mixed (7/22, 31.82%) types. There was a predominance of moderate histological grade tumours (16 grade II) and the average overall survival was 120 days. Positive immunohistochemical staining for epithelial membrane antigen and negative staining for CD-31, p63 and cytokeratin (CK) AE1AE3 in cystic formations confirmed the micropapillary nature of these neoplasms. A proportion of cases exhibited positive epithelial staining for p63 (4/20, 20%) and CK34βE12 (20/22, 90.9%). Most cases were positive for oestrogen (19/20, 95%) and progesterone (19/20, 95%) receptors, but lacked HER-2 (16/22, 72.72%) and epidermal growth factor receptor (15/22, 68.18%) over-expression. The mean proliferation index was 14.8%. The findings demonstrate that, similar to humans, canine IMPCs behave aggressively with high rates of metastasis to regional lymph nodes and short overall survival times.

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).