Lattice-Based Model of Ductal Carcinoma In Situ Suggests Rules for Breast Cancer Progression to an Invasive State

Ductal carcinoma in situ (DCIS) is a heterogeneous group of non-invasive lesions of the breast that result from abnormal proliferation of mammary epithelial cells. Pathologists characterize DCIS by four tissue morphologies (micropapillary, cribriform, solid, and comedo), but the underlying mechanisms that distinguish the development and progression of these morphologies are not well understood. Here we explored the conditions leading to the emergence of the different morphologies of DCIS using a two-dimensional multi-cell lattice-based model that incorporates cell proliferation, apoptosis, necrosis, adhesion, and contractility. We found that the relative rates of cell proliferation and apoptosis governed which of the four morphologies emerged. High proliferation and low apoptosis favored the emergence of solid and comedo morphologies. In contrast, low proliferation and high apoptosis led to the micropapillary morphology, whereas high proliferation and high apoptosis led to the cribriform morphology. The natural progression between morphologies cannot be investigated in vivo since lesions are usually surgically removed upon detection; however, our model suggests probable transitions between these morphologies during breast cancer progression. Importantly, cribriform and comedo appear to be the ultimate morphologies of DCIS. Motivated by previous experimental studies demonstrating that tumor cells behave differently depending on where they are located within the mammary duct in vivo or in engineered tissues, we examined the effects of tissue geometry on the progression of DCIS. In agreement with our previous experimental work, we found that cells are more likely to invade from the end of ducts and that this preferential invasion is regulated by cell adhesion and contractility. This model provides additional insight into tumor cell behavior and allows the exploration of phenotypic transitions not easily monitored in vivo.     

A 2D mechanistic model of breast ductal carcinoma in situ (DCIS) morphology and progression

Ductal carcinoma in situ (DCIS) of the breast is a non-invasive tumor in which cells proliferate abnormally, but remain confined within a duct. Although four distinguishable DCIS morphologies are recognized, the mechanisms that generate these different morphological classes remain unclear, and consequently the prognostic strength of DCIS classification is not strong. To improve the understanding of the relation between morphology and time course, we have developed a 2D in silico particle model of the growth of DCIS within a single breast duct. This model considers mechanical effects such as cellular adhesion and intra-ductal pressure, and biological features including proliferation, apoptosis, necrosis, and cell polarity. Using this model, we find that different regions of parameter space generate distinct morphological subtypes of DCIS, so elucidating the relation between morphology and time course. Furthermore, we find that tumors with similar architectures may in fact be produced through different mechanisms, and we propose future work to further disentangle the mechanisms involved in DCIS progression.     

Pulmonary metastasis of a postradiation breast epithelioid angiosarcoma mimicking adenocarcinoma. A case report

BACKGROUND: Epithelioid angiosarcoma (EAS) is a mesenchymal neoplasm that may appear indistinguishable from carcinoma, melanoma and other tumors with epithelioid/epithelial differentiation. We report a case of metastatic postradiation EAS to the lungs that was mistaken for adenocarcinoma. CASE: A 45-year-old woman who received radiotherapy for ductal carcinoma in situ (DCIS) 5 years previously had a local recurrence a year earlier and recent development of bilateral small pulmonary nodules. Fine needle aspiration biopsy of the lung lesions showed round to oval tumor cells with amphophilic cytoplasm. An interpretation of adenocarcinoma was rendered during assessment for specimen adequacy. The original breast tumor was typical of cribriform DCIS. Review of the recurrent breast tumor (initially reported as DCIS) and a prior wedge resection of the lung nodules (reported as EAS) showed an epithelial-appearing tumor exhibiting an endothelial immunophenotype CONCLUSION: The cytologic features of EAS may resemble those of other neoplasms. In evaluating tumors with epithelioid morphology, mesenchymal tumors should also be considered so that appropriate antibodies can be included in the panel for immunohistochemistry. The importance of reviewing the patient's previous biopsy materials cannot be overemphasized.     

Heterogeneous chromosomal aberrations in intraductal breast lesions adjacent to invasive carcinoma.

There is evidence that breast cancer is a heterogeneous disease phenotypically as well as molecular biologically. So far, heterogeneity on the molecular biological level has not been investigated in potential precursor lesions, such as ductal hyperplasia (DH) and ductal carcinoma in situ (DCIS). In this study we applied comparative genomic hybridization (CGH) to formalin-fixed, paraffin-embedded breast tissue with DH and DCIS, adjacent to invasive ductal carcinoma (IDC), to screen these potential precursor lesions for whole genomic chromosomal imbalances. Laser-microdissection was used to select pure cell populations from the sections. Isolated DNA was amplified by degenerate oligonucleotide primed PCR (DOP-PCR) and further processed for CGH analysis. Investigating multiple samples (n = 25) from four patients we found an average of 5.6 +/- 0.9 (mean +/- SEM) chromosomal imbalances already present in DH. In the twelve DCIS lesions an average of 10.8 (+/- 0.9) aberrations was identified with 14.8 (+/- 0.8) aberrations in the four adjacent IDC lesions. The increasing number of chromosomal changes in parallel with the histopathological sequence corroborate the hypothesis, that the carcinomas may have developed through a sequential progression from normal to proliferative epithelium and eventually into carcinoma. However, heterogeneous results were identified in the multiple samples per entity from the same patient, demonstrated mainly in the DCIS samples in the chromosomal regions 6p, 9p, 11q, 16p and 17q, in the DH samples by 3p, 16p and 17q. This heterogeneous findings were most pronounced within the DH and was less in the DCIS and IDC samples. The only aberration consistently found in all samples-even in all DH sample-was amplification of the 20q13 region. Our results demonstrate, that the applied combination of laser-microdissection, DOP-PCR and CGH, may serve to analyse breast carcinogenesis pathways in suitable histological material. However, so far, it is unclear how to handle heterogeneous results and these make identification of relevant changes more difficult. Setting a threshold and evaluating only those chromosomal changes which are present in a majority of samples may be one possibility. This involves however, the risk that infrequent but possibly significant aberrations may be missed. Figures on http://www.esacp.org/acp/2000/20-1/aubele. htm.     

MAME Models for 4D Live-cell Imaging of Tumor: Microenvironment Interactions that Impact Malignant Progression

We have developed 3D coculture models, which we term MAME (mammary architecture and microenvironment engineering), and used them for live-cell imaging in real-time of cell:cell interactions. Our overall goal was to develop models that recapitulate the architecture of preinvasive breast lesions to study their progression to an invasive phenotype. Specifically, we developed models to analyze interactions among pre-malignant breast epithelial cell variants and other cell types of the tumor microenvironment that have been implicated in enhancing or reducing the progression of preinvasive breast epithelial cells to invasive ductal carcinomas. Other cell types studied to date are myoepithelial cells, fibroblasts, macrophages and blood and lymphatic microvascular endothelial cells. In addition to the MAME models, which are designed to recapitulate the cellular interactions within the breast during cancer progression, we have developed comparable models for the progression of prostate cancers. Here we illustrate the procedures for establishing the 3D cocultures along with the use of live-cell imaging and a functional proteolysis assay to follow the transition of cocultures of breast ductal carcinoma in situ (DCIS) cells and fibroblasts to an invasive phenotype over time, in this case over twenty-three days in culture. The MAME cocultures consist of multiple layers. Fibroblasts are embedded in the bottom layer of type I collagen. On that is placed a layer of reconstituted basement membrane (rBM) on which DCIS cells are seeded. A final top layer of 2% rBM is included and replenished with every change of media. To image proteolysis associated with the progression to an invasive phenotype, we use dye-quenched (DQ) fluorescent matrix proteins (DQ-collagen I mixed with the layer of collagen I and DQ-collagen IV mixed with the middle layer of rBM) and observe live cultures using confocal microscopy. Optical sections are captured, processed and reconstructed in 3D with Volocity visualization software. Over the course of 23 days in MAME cocultures, the DCIS cells proliferate and coalesce into large invasive structures. Fibroblasts migrate and become incorporated into these invasive structures. Fluorescent proteolytic fragments of the collagens are found in association with the surface of DCIS structures, intracellularly, and also dispersed throughout the surrounding matrix. Drugs that target proteolytic, chemokine/cytokine and kinase pathways or modifications in the cellular composition of the cocultures can reduce the invasiveness, suggesting that MAME models can be used as preclinical screens for novel therapeutic approaches.     

Estimation of the deformations induced by articulated bodies: Registration of the spinal column

We present a new non-rigid registration algorithm estimating the displacement field generated by articulated bodies. Indeed the bony structures between different patient images may rigidly move while other tissues may deform in a more complex way. Our algorithm tracks the displacement induced in the column by a movement of the patient between two acquisitions. The volumetric deformation field in the whole body is then inferred from those displacements using a linear elastic biomechanical finite element model. We demonstrate in this paper that this method provides accurate results on 3D sets of computed tomography (CT), MR and positron emission tomography (PET) images and that the results of the registration algorithm show significant decreases in the mean, min and max errors.     

The value of dynamic contrast enhanced breast MRI in mammographically detected BI-RADS 5 microcalcifications

Aims: To evaluate the role of dynamic contrast-enhanced magnetic resonance imaging (MRI) in the diagnosis of BI-RADS-5 type of microcalcifications of the breast, to compare the size of the microcalcification lesions using mammography (MG) and MRI, and to determine the value of MRI in surgery for microcalcifications. The study also determines the morphology of microcalcification lesions, assesses kinetic curves and compare MRI features of ductal carcinoma in situ (DCIS) for different histopathological grades. Methods: Our group consisted of 32 patients with mammographically detected BI-RADS 5 microcalcifications. The MRI was done in this group of women which was later followed by stereotactic vaccum-assisted biopsy (SVAB). Surgery was performed on all patients with a biopsy that resulted in a diagnosis of breast cancer or atypical ductal hyperplasia (ADH). Results: Of our group of 32 patients, there were 35 mammograhically detected microcalcification lesions, 32 DCIS, one ADH and two benign findings according to the final histology. The microcalcification lesions were larger using MRI than in MG in 10 women. We diagnosed DCIS multifocality in 6 women and bilateral carcinoma in one woman. As with kinetic curve assessment, we found in 67 % of DCIS a rapid rise, 27 % a moderate and in 6 % a slow initial rise. With the pattern of enhancement in the delayed phase, we found in 30 % of DCIS a washout pattern, 67 % a plateau and in 3 % a persistent pattern. Noted difference between high and low grade DCIS was confirmed. Conclusions: MRI sensitivity in the detection of DCIS was 94 % in our group of patients and was the sole evidence for detection of multifocality and bilateral incidence of carcinoma. In 26 % of women the outcome of MRI was the most important for converting breast conserving surgery to mastectomy.     

Low-grade cribriform ductal carcinoma in situ of the breast. Fine needle aspiration cytology in three cases.

This paper presents the cytologic features of fine needle aspiration biopsy specimens from three cases of ductal carcinoma in situ characterized by small and uniform tumor cells growing in a predominantly cribriform pattern without comedo necrosis (low-grade cribriform ductal carcinoma in situ). On cytology, most of the tumor cells were clustered in three-dimensional ductal structures. Occasionally in the clusters the tumor cells were seen bordering central lumina, quite similar to the architecture in histology. A few single tumor cells and no myoepithelium were seen. The background was clear or slightly hemorrhagic, without necrosis. The tumor cells were uniform and had a cylindroid shape, with round or oval nuclei. Morphometrically the mean largest nuclear diameter was 1.5-1.6 times that of a red blood cell. The chromatin was finely granular, with a minute nucleolus and slight condensation along the nuclear membrane. In cut sections all three tumors showed strong immunoreactivity for neuron-specific enolase. Unless the cribriform growth pattern is recognized in the smear, the cytologic diagnosis of this entity is difficult.     

Quantification of Dynamic Morphological Drug Responses in 3D Organotypic Cell Cultures by Automated Image Analysis

Glandular epithelial cells differentiate into complex multicellular or acinar structures, when embedded in three-dimensional (3D) extracellular matrix. The spectrum of different multicellular morphologies formed in 3D is a sensitive indicator for the differentiation potential of normal, non-transformed cells compared to different stages of malignant progression. In addition, single cells or cell aggregates may actively invade the matrix, utilizing epithelial, mesenchymal or mixed modes of motility. Dynamic phenotypic changes involved in 3D tumor cell invasion are sensitive to specific small-molecule inhibitors that target the actin cytoskeleton. We have used a panel of inhibitors to demonstrate the power of automated image analysis as a phenotypic or morphometric readout in cell-based assays. We introduce a streamlined stand-alone software solution that supports large-scale high-content screens, based on complex and organotypic cultures. AMIDA (Automated Morphometric Image Data Analysis) allows quantitative measurements of large numbers of images and structures, with a multitude of different spheroid shapes, sizes, and textures. AMIDA supports an automated workflow, and can be combined with quality control and statistical tools for data interpretation and visualization. We have used a representative panel of 12 prostate and breast cancer lines that display a broad spectrum of different spheroid morphologies and modes of invasion, challenged by a library of 19 direct or indirect modulators of the actin cytoskeleton which induce systematic changes in spheroid morphology and differentiation versus invasion. These results were independently validated by 2D proliferation, apoptosis and cell motility assays. We identified three drugs that primarily attenuated the invasion and formation of invasive processes in 3D, without affecting proliferation or apoptosis. Two of these compounds block Rac signalling, one affects cellular cAMP/cGMP accumulation. Our approach supports the growing needs for user-friendly, straightforward solutions that facilitate large-scale, cell-based 3D assays in basic research, drug discovery, and target validation.     

AgNOR analysis of atypical ductal hyperplasia and intraductal carcinoma of the breast

OBJECTIVE: To determine the diagnostic and prognostic value of argyrophilic nucleolar organizer regions (AgNORs) in atypical ductal hyperplasia (ADH), ductal carcinoma in situ (DCIS) and microinvasive ductal carcinoma (MDCA) of the breast. STUDY DESIGN: Image analysis of histologic sections from biopsies of 46 breast ADH and DCIS and 18 cases of MDCA. Determination of morphometric features of cell nuclei and nucleolar organizer regions by using AMBA software system. Data were compared with the estrogen receptor/progesterone receptor (ER/PR) content as well as with the growth fraction, determined immunohistochemically. RESULTS: AgNOR number and total AgNOR area increased from ADH to DCIS. The highest values were recorded in cases of DCIS with microinvasion. Differences between ADH and intraductal or microinvasive ductal carcinoma were statistically significant. Within the group of intraductal carcinomas, the lowest values were measured in the solid type and highest values in the comedo type. A correlation was found between AgNOR features and growth fraction but not between these features and ER/PR status. CONCLUSION: Selected AgNOR features are relevant for differentiation between ADH and DCIS as well as between low and high grade DCIS and microinvasive ductal carcinoma. Therefore, objective and reproducible data obtained by AgNOR analysis may allow better evaluation of the prognostic significance of these lesions.     

Magnetic resonance microscopy of prenatal dolphins (Mammalia, Odontoceti, Delphinidae) - Ontogenetic and phylogenetic implications

The structure of two preserved prenatal dolphins were visualized by 3D MR microscopy (isotropic nominal resolution up to 78.1 μm), which is a high-resolution 3D magnetic resonance imaging (MRI) technique. To determine the benefits and limitations of this method, the acquired 3D datasets were segmented manually and compared to histological sections of different specimens in corresponding developmental stages. The MR images visualize the external and internal morphology of both prenatal dolphins in detail. Various organ systems with their main components are clearly documented in the images, allowing a complete segmentation of the specimens and the calculation of volumes and surface areas of different organ systems. Due to its non-invasive character and the detailed imaging within its resolution range, MR microscopy proves to be a valuable tool in developmental biology for the visualization of the inner architecture of rare and delicate museum specimens, such as the small dolphin embryo and fetus examined. In these two prenatal dolphins, the profound structural modifications at the transition from the embryonic to the fetal stage reflect the adaptations of the mammalian bauplan to the requirements of a holaquatic cetacean life-style. However, the developmental pattern and sequence of the emerging tissues and organs in prenatal life do not resemble the hypothesized evolution of the structural and functional adaptations found in the fossil record.     

Template matching as a tool for annotation of tomograms of stained biological structures

In recent years, electron tomography has improved our three-dimensional (3D) insight in the structural architecture of cells and organelles. For studies that involve the 3D imaging of stained sections, manual annotation of tomographic data has been an important method to help understand the overall 3D morphology of cellular compartments. Here, we postulate that template matching can provide a tool for more objective annotation and contouring of cellular structures. Also, this technique can extract information hitherto unharvested in tomographic studies. To evaluate the performance of template matching on tomograms of stained sections, we generated several templates representing a piece of microtubule or patches of membranes of different staining-thicknesses. These templates were matched to tomograms of stained electron microscopy sections. Both microtubules and ER-Golgi membranes could be detected using this method. By matching cuboids of different thicknesses, we were able to distinguish between coated and non-coated endosomal membrane-domains. Finally, heterogeneity in staining-thickness of endosomes could be observed. Template matching can be a useful addition to existing annotation-methods, and provide additional insights in cellular architecture.     

A quantitative theoretical model for the development of malignancy in ductal carcinoma in situ

Mathematical models and clinical observations have demonstrated that microenvironmental hypoxia and acidosis are important selection factors during the later stages of the somatic evolution of breast cancer. The consequent promotion of constitutive upregulation of glycolysis and resistance to acid-induced cellular toxicity is hypothesized to be critical for the ability of cancer cells to invade host tissue. In this work we developed a 3D fixed lattice cellular automata model to study the role of these two phenotypes in determining morphology and the potential for invasion of ductal carcinoma in situ (DCIS), which in this work is defined as the erosion of a healthy epithelial cell layer and direct contact with the basement membrane. The model was conceived as a 40-cell wide epithelial duct surrounded by blood vessels and composed of a basement membrane and one internal layer of epithelial cells. Our results show that an increment in the order of 8-fold in glucose metabolism and an increase in acid resistance corresponding to pH thresholds of approximately 6.8 and 6.45 for quiescence and death, respectively, are required for the tumor to breach through the layer of healthy epithelial cells and reach the basement membrane as a first step for invasion. Our model also suggests correlations between classic morphologies and different values of hyperglycolytic and acid-resistant phenotypes, indicating that immunohistochemistry studies targeting these genes may improve the predictive power of morphological analyses of biopsies.     

Carcinoma in situ of the female breast. A clinico-pathological,immunohistological, and DNA ploidy study

Carcinoma in situ of the breast (CIS) comprise a heterogenous group of lesions, covering a wide spectrum of clinical conditions and histopathological changes. With respect to biological behavior, CIS range from biologically aggressive lesions with a substantial risk of progression into invasive carcinoma (IC), to lesions with a very low malignant potential. Two main types of CIS are described--ductal carcinoma in situ (DCIS) and lobular carcinoma in situ (LCIS). Previous studies of CIS indicate that approximately a third will subsequently develop IC. Autopsy studies indicate that CIS is frequently occurring and it was estimated that about 20% of all women will develop CIS during lifetime. Only a minor fraction is ever diagnosed, although the incidence of DCIS is increasing, especially related to mammography screening. The lack of knowledge about the biological significance of the histopathological subtypes was the background of the present study. In 1982, a nationwide, prospective study of CIS (protocol DBCG 82-IS) was initiated by the Danish Breast Cancer Cooperative Group (DBCG). From this protocol, the group of patients treated with breast conservation surgery (BCS) constituted the material for clinico-histological investigation. A total of 275 women were included in the period 1982-89. Follow-up studies showed that recurrence rate was significantly related to nuclear size of the primary lesion. Since nuclear changes might be related to DNA content and, furthermore, many invasive breast carcinomas were shown to be DNA aneuploid, flow cytometric (FCM) DNA ploidy analysis was performed in a series of DCIS lesions. More than 80% of these lesions were DNA aneuploid, with a distribution similar to that found in invasive carcinomas. This finding raised the hypothesis that the DNA pattern of an invasive carcinoma was already established at the preinvasive stage of DCIS. Therefore, FCM DNA analysis was performed on a series of ICs with predominance of DCIS. Partial or complete concordance in DNA ploidy between DCIS and IC within the individual case was found in most cases, except for the additional presence in the IC component of DNA hyperdiploid clones that might possibly be of importance for the process of invasion. In order to further characterize CIS lesions and, possibly, to discriminate biologically different groups, immunohistochemical markers were investigated in a consecutive series of CIS and IC with predominance of DCIS. The results were correlated to the histopathological and DNA ploidy findings. In DCIS, significant correlation was shown between large nuclear size and comedonecrosis, both of which showed also strong association to DNA aneuploidy, high proliferation activity, low steroid receptor content, and overexpression of c-erbB-2 and p53--factors that may indicate an aggressive behavior. Small nuclear CIS, whether LCIS or DCIS, on the contrary, were DNA diploid with low proliferation, and no cases showed overexpression of c-erbB-2 and p53. In IC, comparison of the DCIS and the invasive component showed similar patterns. No significant differences, in neither morphology, immunohistochemistry, nor DNA ploidy, were shown between DCIS without and with invasion. These findings may indicate that none of the parameters in question may on its own be essential for the decisive event of invasive growth.     

Domain tree-based analysis of protein architecture evolution

Understanding the dynamics behind domain architecture evolution is of great importance to unravel the functions of proteins. Complex architectures have been created throughout evolution by rearrangement and duplication events. An interesting question is how many times a particular architecture has been created, a form of convergent evolution or domain architecture reinvention. Previous studies have approached this issue by comparing architectures found in different species. We wanted to achieve a finer-grained analysis by reconstructing protein architectures on complete domain trees. The prevalence of domain architecture reinvention in 96 genomes was investigated with a novel domain tree-based method that uses maximum parsimony for inferring ancestral protein architectures. Domain architectures were taken from Pfam. To ensure robustness, we applied the method to bootstrap trees and only considered results with strong statistical support. We detected multiple origins for 12.4% of the scored architectures. In a much smaller data set, the subset of completely domain-assigned proteins, the figure was 5.6%. These results indicate that domain architecture reinvention is a much more common phenomenon than previously thought. We also determined which domains are most frequent in multiply created architectures and assessed whether specific functions could be attributed to them. However, no strong functional bias was found in architectures with multiple origins.     

Automated cell nuclear segmentation in color images of hematoxylin and eosin-stained breast biopsy

OBJECTIVE: To develop an automated, reproducible epithelial cell nuclear segmentation method to quantify cytologic features quickly and accurately from breast biopsy. STUDY DESIGN: The method, based on fuzzy c-mean clustering of the hue-band of color images and the watershed transform, was applied to 39 images from 3 histologic types (typical hyperplasia, atypical hyperplasia, and ductal carcinoma in situ [cribriform and solid]). RESULTS: The performance of the segmentation algorithm was evaluated by visually determining the percentage of badly segmented nuclei (approximately 25% for all types), the percentage of nuclei that remained in clumps (4.5-16.7%) and the percentage of missed nuclei (0.4-1.5%) for each image. CONCLUSION: The segmentation algorithm was sensitive in that a small percentage of nuclei were missed. However, the percentage of badly segmented nuclei was on the order of 25%, and the percentage of nuclei that remained in clumps was on the order of 10% of the total number of nuclei in the duct. Even so, > 600 nuclei per duct, on average, were segmented correctly; that was a sufficient number by which to calculate accurate quantitative, cytologic, morphometric measurements of epithelial cell nuclei in stained tissue sections of breast biopsy.     

Morphology of fibroblasts in collagen gels: a study using 400 keV electron microscopy and computer graphics

We have used 400 kilovolt intermediate voltage electron microscopy (IVEM) to examine thick sections of fibroblasts cultured in collagen gels. In these 3D collagen lattices, the long, narrow pseudopodial extensions that extend out and make contact with the collagen matrix exhibit a complex topography not seen in the processes put out by cells moving on planar substrata. For this reason, sections 1 to 2 microns thick that enclose a whole cell process are more informative of the overall morphology of the interaction between cells and the collagen than are thin sections. To aid the discrimination of topography of cell processes in stereo views of micrographs, some cells were labeled with antibodies and protein A-colloidal gold conjugates. The gold particles provided clear 3D reference points for computer-aided reconstructions of membrane topography from tilt series of IVEM images. Our results confirm that cells that move through collagen lattices lack the well-spread morphology of their counterparts moving on glass. They are generally rather spindly with several long branching anterior pseudopodia. We found that the cell bodies and major pseudopodial processes were cylindrical, as one might expect of cells in a 3D environment, but at the leading edge of advancing pseudopodia there are small flat extensions similar to those seen in cells on glass. This similarity suggests that the lamellipodium is a basic type of protrusive structure used by fibroblasts during locomotion on all types of substratum. The flattened shape of lamellipodia may be part of the mechanism by which cells sense the orientation of fibrillar extracellular matrices during embryonic morphogenesis.     

Lapatinib inhibits stem/progenitor proliferation in preclinical in vitro models of ductal carcinoma in situ (DCIS)

Breast-conserving surgery for ductal carcinoma in situ (DCIS) is often combined with irradiation, reducing recurrence rates to 20% within 10 years; however, there is no change in overall survival. Evidence in the invasive breast indicates that breast cancer stem cells (CSCs) are radiotherapy-resistant and are capable of re-initiating a tumor recurrence; hence, targeting CSCs in high risk DCIS patient may improve survival. HER2 is overexpressed in 20% of DCIS and is known to be highly active in breast CSCs; we therefore investigated the effect of Lapatinib on DCIS CSC activity using 2 in vitro culture systems. Two DCIS cell lines DCIS.com (HER2 normal) and SUM225 (HER2 overexpressed) as well as DCIS cells from patient samples (n = 18) were cultured as mammospheres to assess CSC activity and in differentiated 3D-matrigel culture to determine effects within the non-CSCs. Mammosphere formation was reduced regardless of HER2 status, although this was more marked within the HER2-positive samples. When grown as differentiated DCIS acini in 3D-matrigel culture, Lapatinib only reduced acini size in the HER2-positive samples via decreased proliferation. Further investigation revealed lapatinib did not reduce self-renewal activity in the CSC population, but their proliferation was decreased regardless of HER2 status. In conclusion we show Lapatinib can reduce DCIS CSC activity, suggesting that the use of Lapatinib in high-risk DCIS patients has the potential to reduce recurrence and the progression of DCIS to invasive disease.