Different types of microcalcifications observed in breast pathology. Correlations with histopathological diagnosis and radiological examination of operative specimens

Microcalcification detectability in breast CT images using CNN observers

BACKGROUND

Breast computed tomography (CT) is an emerging breast imaging modality, and ongoing developments aim to improve breast CT's ability to detect microcalcifications. To understand the effects of different parameters on microcalcification detectability, a virtual clinical trial study was conducted using hybrid images and convolutional neural network (CNN)-based model observers. Mathematically generated microcalcifications were embedded into breast CT data sets acquired at our institution, and parameters related to calcification size, calcification contrast, cluster diameter, cluster density, and image display method (i.e., single slices, slice averaging, and maximum-intensity projections) were evaluated for their influence on microcalcification detectability.

PURPOSE

To investigate the individual effects and the interplay of parameters affecting microcalcification detectability in breast CT.

METHODS

Spherical microcalcifications of varying diameters (0.04, 0.10, 0.15, 0.20, 0.25, 0.30, 0.35, 0.40 mm) and native intensities were computer simulated to portray the partial volume effects of the imaging system. Calcifications were mathematically embedded into 109 patient breast CT volume data sets as individual calcifications or as clusters of calcifications. Six numbers of calcifications (1, 3, 5, 7, 10, 15) distributed within six cluster diameters (1, 3, 5, 6, 8, 10 mm) were simulated to study the effect of cluster density. To study the role of image display method, 2D regions of interest (ROIs) and 3D volumes of interest (VOIs) were generated using single slice extraction, slice averaging, and maximum-intensity projection (MIP). 2D and 3D CNNs were trained on the ROIs and VOIs, and receiver operating characteristic (ROC) curve analysis was used to evaluate detection performance. The area under the ROC curve (AUC) was used as the primary performance metric.

RESULTS

Detection performance decreased with increasing section thickness, and peak detection performance occurred using the native section thickness (0.2 mm) and MIP display. The MIP display method, despite using a single slice, yielded comparable performance to the native section thickness, which employed 50 slices. Reduction in slices did not sacrifice detection accuracy and provided significant computational advantages over multi-slice image volumes. Larger cluster diameters resulted in reduced overall detectability, while smaller cluster diameters led to increased detectability. Additionally, we observed that the presence of more calcifications within a cluster improved the overall detectability, while fewer calcifications decreased it.

CONCLUSIONS

As breast CT is still a relatively new breast imaging modality, there is an ongoing need to identify optimal imaging protocols. This work demonstrated the utility of MIP presentation for displaying image volumes containing microcalcification clusters. It is likely that human observers may also benefit from viewing MIPs compared to individual slices. The results of this investigation begin to elucidate how model observers interact with microcalcification clusters in a 3D volume, and will be useful for future studies investigating a broader set of parameters related to breast CT.

Multicellular spheroids containing synthetic mineral particles: an advanced 3D tumor model system to investigate breast precancer malignancy potential according to the mineral type

Mineral particles that form in soft tissues in association with disease conditions are heterogeneous in their composition and physiochemical properties. Hence, it is challenging to study the effect of mineral type on disease progression in a high-throughput and realistic manner. For example, most early breast precancer lesions, termed ductal carcinoma in situ (DCIS), contain microcalcifications (MCs), calcium-containing pathological minerals. The most common type of MCs is calcium phosphate crystals, mainly carbonated apatite; it is associated with either benign or malignant lesions. In vitro studies indicate that the crystal properties of apatite MCs can affect breast cancer progression. A less common type of MCs is calcium oxalate dihydrate (COD), which is almost always found in benign lesions. We developed a 3D tumor model of multicellular spheroids of human precancer cells containing synthetic MC analogs that link the crystal properties of MCs with the progression of breast precancer to invasive cancer. Using this 3D model, we show that apatite crystals induce Her2 overexpression in DCIS cells. This tumor-triggering effect is increased when the carbonate fraction in the MCs decreases. COD crystals, in contrast, decrease Her2 expression in the spheroids, even compared with a control group with no added MC analogs. Furthermore, COD decreases cell proliferation and migration in DCIS monolayers compared to untreated cells and cells incubated with apatite crystals. This finding suggests that COD is not randomly located only in benign lesions-it may actively contribute to suppressing precancer progression in its surroundings. Our model provides an easy-to-manipulate platform to better understand the interactions between mineral particles and their biological microenvironment. A better understanding of the effect of the crystal properties of MCs on precancer progression will potentially provide new directions for better precancer prognosis and treatment.

Detection of microcalcifications using nonlinear beamforming techniques

OBJECTIVE

Abundant research demonstrates that early detection of cancer leads to improved patient prognoses. By detecting cancer earlier, when tumors are in their primary stages, treatment can be applied before metastases have occurred. The presence of microcalcifications (MCs) is indicative of malignancy in the breast, i.e., 30-50% of all nonpalpable breast cancers detected using mammograms are based on identifying the presence of MCs. Therefore, improving the ability to detect MCs with modern imaging technology remains an important goal. Specifically, improving the sensitivity of ultrasound imaging techniques to detect MCs in the breast will provide an important role for the early detection and diagnosis of breast cancer.

METHODS

In this work, a novel nonlinear beamforming technology for ultrasonic arrays is investigated for its ability to detect MCs. The beamforming technique, called null subtraction imaging (NSI), utilizes nulls in the beam pattern to create images using ultrasound. NSI provides improved lateral resolution, a reduction in side lobes, and an accentuation of bright singular targets. Therefore, it was hypothesized that the use of NSI would result in identification of more MCs in rat tumors having a speckle background. To test this hypothesis, rats with tumors were injected with Hydroxyapatite (HA) particles to mimic MCs. Ultrasound was used to scan the rat tumors and images were constructed using conventional delay and sum and using NSI beamforming. Three readers with experience in diagnostic ultrasound imaging examined the 1,344 images and scored the presence or absence of MCs.

DISCUSSION

In all, 336 different tumor image slices were recorded and each reconstructed using NSI or conventional delay and sum with Hann apodization. In every image where one or MCs were detected in the Hann reconstructions, MCs were detected in the NSI images. In nine rat tumor images, one or more MCs were detected in the NSI images but not in the Hann images.

CONCLUSIONS

Statistically, the results did support the hypothesis that NSI would increase the number of MCs detected in the rat tumors.

Raman analysis of microcalcifications in male breast cancer

Microcalcifications (MCs) are important disease markers for breast cancer. Many studies were conducted on their characterization in female breast cancer (FBC), but no information is available on their composition in male breast cancer (MBC). Raman spectroscopy (RS) is a molecular spectroscopy that can rapidly explore the biochemical composition of MCs without requiring any staining protocol. In this study, we optimized an algorithm to identify the mineral components present in MCs from Raman images. The algorithm was then used to study and compare MCs identified on breast cancer pieces from male and female patients. In total, we analyzed 41 MCs from 5 invasive MBC patients and 149 MCs from 13 invasive FBC patients. Results show that hydroxyapatite is the most abundant type of calcium both in MBC and FBC. However, some differences in the amount and distribution of calcium minerals are present between the two groups. Besides, we observed that MCs in MBC have a higher amount of organic material (collagen) than FBC. To the best of our knowledge, this study provides the first overview of the composition of MCs present in MBC patients; and suggests that these patients have specific features that differentiate them from the previously studied FBC. Our result support thus the need for studies designed explicitly to the understanding of MBC.

Fabrication of microcalcifications for insertion into phantoms used to evaluate x-ray breast imaging systems

Physical breast phantoms can be used to evaluate x-ray imaging systems such as mammography, digital breast tomosynthesis and dedicated breast computed tomography (bCT). These phantoms typically attempt to mimic x-ray attenuation properties of adipose and fibroglandular tissues within the breast. In order to use these phantoms for task-based objective assessment of image quality, relevant diagnostic features should be modeled within the phantom, such as mass lesions and/or microcalcifications. Evaluating imaging system performance in detecting microcalcifications is of particular interest due to its' clinical significance. Many previously-developed phantoms have used materials that model microcalcifications using unrealistic chemical composition, which do not accurately portray their desired x-ray attenuation and scatter properties. We report here on a new method for developing real microcalcification simulants that can be embedded in breast phantoms. This was achieved in several steps, including cross-linking hydroxyapatite and calcium oxalate powders with a binder called polyvinylpyrrolidone (PVP), and mechanical compression. The fabricated microcalcifications were evaluated by measuring their x-ray attenuation and scatter properties using x-ray spectroscopy and x-ray diffraction systems, respectively, and were demonstrated with x-ray mammography and bCT images. Results suggest that using these microcalcification models will make breast phantoms more realistic for use in evaluating task-based detection performance of the abovementioned breast imaging techniques, and bode well for extending their use to spectral imaging and x-ray coherent scatter computed tomography.

Exploring CNN potential in discriminating benign and malignant calcifications in conventional and dual-energy FFDM: simulations and experimental observations

Purpose: Deep convolutional neural networks (CNN) have demonstrated impressive success in various image classification tasks. We investigated the use of CNNs to distinguish between benign and malignant microcalcifications, using either conventional or dual-energy mammography x-ray images. The two kinds of calcifications, known as type-I (calcium oxalate crystals) and type-II (calcium phosphate aggregations), have different attenuation properties in the mammographic energy range. However, variations in microcalcification shape, size, and density as well as compressed breast thickness and breast tissue background make this a challenging discrimination task for the human visual system. Approach: Simulations (conventional and dual-energy mammography) and phantom experiments (conventional mammography only) were conducted using the range of breast thicknesses and randomly shaped microcalcifications. The off-the-shelf Resnet-18 CNN was trained on the regions of interest with calcification clusters of the two kinds. Results: Both Monte Carlo simulations and experimental phantom data suggest that deep neural networks can be trained to separate the two classes of calcifications with high accuracy, using dual-energy mammograms. Conclusions: Our work shows the encouraging results of using the CNNs for non-invasive testing for type-I and type-II microcalcifications and may stimulate further research in this area with expanding presence of the novel breast imaging modalities like dual-energy mammography or systems using photon-counting detectors.

Coherent anti-Stokes Raman scattering imaging of microcalcifications associated with breast cancer

Chemical imaging of calcifications was demonstrated in the depth of a tissue. Using long wavelength excitation, broadband coherent anti-Stokes Raman scattering and hierarchical cluster analysis, imaging and chemical analysis were performed 2 mm below the skin level in a model system. Applications to breast cancer diagnostics and imaging are discussed together with the methods to further extend the depth and improve the spatial resolution of chemical imaging.

Quantitative chemical imaging of breast calcifications in association with neoplastic processes

Calcifications play an essential role in early breast cancer detection and diagnosis. However, information regarding the chemical composition of calcifications identified on mammography and histology is limited. Detailed spectroscopy reveals an association between the chemical composition of calcifications and breast cancer, warranting the development of novel analytical tools to better define calcification types. Previous investigations average calcification composition across broad tissue sections with no spatially resolved information or provide qualitative visualization, which prevents a robust linking of specific spatially resolved changes in calcification chemistry with the pathologic process.

Method: To visualize breast calcification chemical composition at high spatial resolution, we apply hyperspectral stimulated Raman scattering (SRS) microscopy to study breast calcifications associated with a spectrum of breast changes ranging from benign to neoplastic processes, including atypical ductal hyperplasia, ductal carcinoma in situ, and invasive ductal carcinoma. The carbonate content of individual breast calcifications is quantified using a simple ratiometric analysis.

Results: Our findings reveal that intra-sample calcification carbonate content is closely associated with local pathological processes. Single calcification analysis supports previous studies demonstrating decreasing average carbonate level with increasing malignant potential. Sensitivity and specificity reach >85% when carbonate content level is used as the single differentiator in separating benign from neoplastic processes. However, the average carbonate content is limiting when trying to separate specific diagnostic categories, such as fibroadenoma and invasive ductal carcinoma. Second harmonic generation (SHG) data can provide critical information to bridge this gap.

Conclusion: SRS, combined with SHG, can be a valuable tool in better understanding calcifications in carcinogenesis, diagnosis, and possible prognosis. This study not only reveals previously unknown large variations of breast microcalcifications in association with local malignancy but also corroborates the clinical value of linking microcalcification chemistry to breast malignancy. More importantly, it represents an important step in the development of a label-free imaging strategy for breast cancer diagnosis with tremendous potential to address major challenges in diagnostic discordance in pathology.

Raman Spectroscopy Reveals That Biochemical Composition of Breast Microcalcifications Correlates with Histopathologic Features

Breast microcalcifications are a common mammographic finding. Microcalcifications are considered suspicious signs of breast cancer and a breast biopsy is required, however, cancer is diagnosed in only a few patients. Reducing unnecessary biopsies and rapid characterization of breast microcalcifications are unmet clinical needs. In this study, 473 microcalcifications detected on breast biopsy specimens from 56 patients were characterized entirely by Raman mapping and confirmed by X-ray scattering. Microcalcifications from malignant samples were generally more homogeneous, more crystalline, and characterized by a less substituted crystal lattice compared with benign samples. There were significant differences in Raman features corresponding to the phosphate and carbonate bands between the benign and malignant groups. In addition to the heterogeneous composition, the presence of whitlockite specifically emerged as marker of benignity in benign microcalcifications. The whole Raman signature of each microcalcification was then used to build a classification model that distinguishes microcalcifications according to their overall biochemical composition. After validation, microcalcifications found in benign and malignant samples were correctly recognized with 93.5% sensitivity and 80.6% specificity. Finally, microcalcifications identified in malignant biopsies, but located outside the lesion, reported malignant features in 65% of in situ and 98% of invasive cancer cases, respectively, suggesting that the local microenvironment influences microcalcification features. This study confirms that the composition and structural features of microcalcifications correlate with breast pathology and indicates new diagnostic potentialities based on microcalcifications assessment. SIGNIFICANCE: Raman spectroscopy could be a quick and accurate diagnostic tool to precisely characterize and distinguish benign from malignant breast microcalcifications detected on mammography.

Dual Energy X-ray Methods for the Characterization, Quantification and Imaging of Calcification Minerals and Masses in Breast

Dual energy (DE) technique has been used by numerous studies in order to detect breast cancer in early stages. Although mammography is the gold standard, the dual energy technique offers the advantage of the suppression of the contrast between adipose and glandular tissues and reveals pathogenesis that is not present in conventional mammography. Both dual energy subtraction and dual energy contrast enhanced techniques were used in order to study the potential of dual energy technique to assist in detection or/and visualization of calcification minerals, masses and lesions obscured by overlapping tissue. This article reviews recent developments in this field, regarding: i) simulation studies carried out for the optimizations of the dual energy technique used in order to characterize and quantify calcification minerals or/and visualize suspected findings, and ii) the subsequent experimental verifications, and finally, the adaptation of the dual energy technique in clinical practice.

New advance in breast cancer pathology and imaging

The improvement of knowledge concerning the pathology of breast cancer could provide the rationale for the development of new imaging diagnostic protocols. Indeed, as for the microcalcifications, new histopathological markers can be used as target for in vivo early detection of breast cancer lesions by using molecular imaging techniques such as positron emission tomography. Specifically, the mutual contribution of these medical specialties can ‘nourish’ the dream of a personalized medicine that takes into account the intrinsic variability of breast cancer. In this review, we report the main discoveries concerning breast cancer pathology highlighting the possible cooperation between the departments of anatomic pathology and imaging diagnostics.

Malignancy rates of stereotactic biopsies of two or more distinct sites of suspicious calcifications in women without known breast cancer

OBJECTIVE

To determine the malignancy rate in women without a concurrent breast cancer diagnosis at presentation who underwent stereotactic biopsies of distinct sites of suspicious calcifications.

METHODS

This retrospective study included 280 women without a concurrent breast cancer diagnosis who underwent 587 stereotactic biopsies of two or more distinct sites of suspicious calcifications in one or both breasts at our institution from 2010 to 2015.

RESULTS

The overall malignancy rate was 27.9% (78/280, 95% CI, 22.7%-33.5%) at the patient level and 18.7% (110/587, 95% CI, 15.7%-22.1%) at the lesion level. Eighteen had invasive cancers (mean [range] diameter, 0.5 cm [0.1-1.7]; six grade I, ten grade II, two grade III), one of whom had multifocal and another bilateral malignancy. Sixty had ductal carcinoma in situ. Of the 171 with all calcifications of the same morphology, 139 (81.3%) had all calcifications in the same pathology category (benign, high-risk, or malignant).

CONCLUSION

The malignancy rate is substantial in women who undergo stereotactic biopsies of two or more distinct calcification sites. Given the nearly 20% rate of dissimilar histopathology between calcification sites with similar morphology, if only one site is biopsied and results in a malignant pathology, biopsy of the additional calcifications is warranted. Even if the pathology result of the one site biopsy is benign, biopsy of additional sites may perhaps still be necessary.

Classification of breast microcalcifications using dual-energy mammography

The potential of dual-energy mammography for microcalcification classification was investigated with simulation and phantom studies. Classification of type I/II calcifications was performed using the tissue attenuation ratio as a performance metric. The simulation and phantom studies were carried out using breast phantoms of 50% fibroglandular and 50% adipose tissue composition and thicknessess ranging from 3 to 6 cm. The phantoms included models of microcalcifications ranging in size between 200 and 900    μ m . The simulation study was carried out with fixed MGD of 1.5 mGy using various low- and high-kVp spectra, aluminum filtration thicknesses, and exposure distribution ratios to predict an optimized imaging protocol for the phantom study. Attenuation ratio values were calculated for microcalcification signals of different types at two different voltage settings. ROC analysis showed that classification performance as indicated by the area under the ROC curve was always greater than 0.95 for 1.5 mGy deposited mean glandular dose. This study provides encouraging first results in classifying malignant and benign microcalcifications based solely on dual-energy mammography images.

Correlative imaging reveals physiochemical heterogeneity of microcalcifications in human breast carcinomas

Microcalcifications (MCs) are routinely used to detect breast cancer in mammography. Little is known, however, about their materials properties and associated organic matrix, or their correlation to breast cancer prognosis. We combine histopathology, Raman microscopy, and electron microscopy to image MCs within snap-frozen human breast tissue and generate micron-scale resolution correlative maps of crystalline phase, trace metals, particle morphology, and organic matrix chemical signatures within high grade ductal carcinoma in situ (DCIS) and invasive cancer. We reveal the heterogeneity of mineral-matrix pairings, including punctate apatitic particles (<2 µm) with associated trace elements (e.g., F, Na, and unexpectedly Al) distributed within the necrotic cores of DCIS, and both apatite and spheroidal whitlockite particles in invasive cancer within a matrix containing spectroscopic signatures of collagen, non-collagen proteins, cholesterol, carotenoids, and DNA. Among the three DCIS samples, we identify key similarities in MC morphology and distribution, supporting a dystrophic mineralization pathway. This multimodal methodology lays the groundwork for establishing MC heterogeneity in the context of breast cancer biology, and could dramatically improve current prognostic models.

Non-invasive classification of breast microcalcifications using x-ray coherent scatter computed tomography

We investigate the use of energy dispersive x-ray coherent scatter computed tomography (ED-CSCT) as a non-invasive diagnostic method to differentiate between type I and type II breast calcifications. This approach is sensitive to the differences of composition and internal crystal structure of different types of microcalcifications. The study is carried out by simulating a CSCT system with a scanning pencil beam, considering a polychromatic x-ray source and an energy-resolving photon counting detector. In a first step, the multidimensional angle and energy distributed CSCT data is reduced to the projection-space distributions of only a few components, corresponding to the expected target composition: adipose, glandular tissue, weddellite (calcium oxalate) for type I calcifications, and hydroxyapatite for type II calcifications. The maximum-likelihood estimation of scatter components algorithm used, operating in the projection space, takes into account the polychromatic source, the detector response function and the energy dependent attenuation. In the second step, component images are reconstructed from the corresponding estimated component projections using filtered backprojection. In a preliminary step the coherent scatter differential cross sections for hydroxyapatite and weddellite minerals were determined experimentally. The classification of type I or II calcifications is done using the relative contrasts of their components as the criterion. Simulation tests were carried out for different doses and energy resolutions for multiple realizations. The results were analyzed using relative/receiver operating characteristic methodology and show good discrimination ability at medium and higher doses. The noninvasive CSCT technique shows potential to further improve the breast diagnostic accuracy and reduce the number of breast biopsies.

Polarizable crystals in apocrine sweat gland tumors: A series of 3 cases

Polarizable calcium oxalate (CaOx) crystals have been well documented in breast biopsies, generally associated with benign apocrine metaplasia. In contrast, polarizable crystals are only rarely reported in skin adnexal neoplasms. We report 3 different cases of sweat gland tumors with polarizable crystals morphologically suggestive of CaOx: 1 apocrine hidrocystoma and 2 tubular apocrine adenomas. The histologic features were examined in 3 cases. Clinical presentation summary included 2 males and 1 female, ages 53 to 74 years, with lesions located on the left cheek, inferior vertex scalp and the left eyebrow. All 3 cases showed polarizable, geometric, plate-like and fractured, colorless crystals within the lumens of the neoplasm. Of note, these crystals were seen only on the toluidine blue-stained section of Case #1, but were not present on the corresponding permanent section. We hypothesize that polarizable crystals may be present in sweat gland neoplasms more often than previously documented, but that they may often dissolve with routine processing, accounting for their rare visibility. We highlight this rare finding, and suggest that it may be underreported. We only noted this finding in benign apocrine tumors; further investigation would be necessary to determine whether these crystals are also seen in other cutaneous adnexal neoplasms.

Contrast-enhanced X-ray detection of breast microcalcifications in a murine model using targeted gold nanoparticles

Microcalcifications are deposits of hydroxyapatite (HA) mineral within breast tissue and the most common abnormality detected by mammography when screening for breast cancer due to exhibiting greater X-ray attenuation than the surrounding tissue. However, the detection of microcalcifications is limited by the sensitivity and specificity of mammography. Therefore, the objective of this study was to investigate in vivo targeted delivery of bisphosphonate-functionalized gold nanoparticles (BP-Au NPs) for contrast-enhanced detection of microcalcifications using computed tomography (CT). A murine model was developed for precise, a priori control over the level of microcalcification burden by injecting varying concentrations of HA crystals in a Matrigel carrier into mammary glands. The measured X-ray attenuation of microcalcifications containing varying HA concentrations demonstrated that the model was reproducible and able to recapitulate varying levels of microcalcification burden, including levels undetectable by CT in the absence of contrast enhancement. After intramammary delivery, BP-Au NPs provided enhanced contrast for the detection of microcalcifications that were otherwise below the CT detection limit. BP-Au NPs targeted microcalcifications due to specific binding to HA crystal surfaces, resulting in contrast between the HA microcalcification site and surrounding tissue which was visibly apparent (∼30-135 HU) within 2 days after delivery. Therefore, targeted BP-Au NPs enabled improved sensitivity and specificity for the detection of microcalcifications.

Bisphosphonate-functionalized gold nanoparticles for contrast-enhanced X-ray detection of breast microcalcifications

Microcalcifications are one of the most common abnormalities detected by mammography for the diagnosis of breast cancer. However, the detection of microcalcifications and correct diagnosis of breast cancer are limited by the sensitivity and specificity of mammography. Therefore, the objective of this study was to investigate the potential of bisphosphonate-functionalized gold nanoparticles (BP-Au NPs) for contrast-enhanced radiographic detection of breast microcalcifications using two models of breast microcalcifications, which allowed for precise control over levels of hydroxyapatite (HA) mineral within a low attenuating matrix. First, an in vitro imaging phantom was prepared with varying concentrations of HA uniformly dispersed in an agarose hydrogel. The X-ray attenuation of HA-agarose compositions labeled by BP-Au NPs was increased by up to 26 HU compared to unlabeled compositions for HA concentrations ranging from 1 to 10 mg/mL. Second, an ex vivo tissue model was developed to more closely mimic the heterogeneity of breast tissue by injecting varying concentrations of HA in a Matrigel carrier into murine mammary glands. The X-ray attenuation of HA-Matrigel compositions labeled by BP-Au NPs was increased by up to 289 HU compared to unlabeled compositions for HA concentrations ranging from 0.5 to 25 mg/mL, which included an HA concentration (0.5 mg/mL) that was otherwise undetectable by micro-computed tomography. Cumulatively, both models demonstrated the ability of BP-Au NPs to enhance contrast for radiographic detection of microcalcifications, including at a clinically-relevant imaging resolution. Therefore, BP-Au NPs may have potential to improve clinical detection of breast microcalcifications by mammography.

Osteotropic cancer diagnosis by an osteocalcin inspired molecular imaging mimetic

BACKGROUND

Although microcalcifications of hydroxyapatite can be found in both benign and malignant osteotropic tumors, they are mostly seen in proliferative lesions, including carcinoma. The aim of this present study is to develop a molecular imaging contrast agent for selective identification of hydroxyapatite calcification in human osteotropic tumor tissues ex vivo and in human osteosarcoma cells in vitro.

METHODS

A bioinspired biomarker, hydroxyapatite binding peptide (HABP), was designed to mimic natural protein osteocalcin property in vivo. A fluorescein isothiocyanate dye conjugated HABP (HABP-19) was utilized to characterize hydroxyapatite on human osteotropic tumor tissue sections ex vivo and to selectively image hydroxyapatite calcifications in human osteosarcoma cells in vitro.

RESULTS

Using a HABP-19 molecular imaging probe, we have shown that it is possible to selectively image hydroxyapatite calcifications in osteotropic cancers ex vivo and in human SaOS-2 osteosarcoma cells in vitro.

CONCLUSION

Hydroxyapatite calcifications were selectively detected in osteotropic tissues ex vivo and in the early stage of the calcification process of SaOS-2 human osteosarcoma in vitro using our HABP-19 molecular imaging probe. This new target-selective molecular imaging probe makes it possible to study the earliest events associated with hydroxyapatite deposition in various osteotropic cancers at the cellular and molecular levels.

GENERAL SIGNIFICANCE

It potentially could be used to diagnose and treat osteotropic cancer or to anchor therapeutic agents directing the local distribution of desired therapy at calcified sites.

Comparison of the x-ray attenuation properties of breast calcifications, aluminium, hydroxyapatite and calcium oxalate

Aluminium is often used as a substitute material for calcifications in phantom measurements in mammography. Additionally, calcium oxalate, hydroxyapatite and aluminium are used in simulation studies. This assumes that these materials have similar attenuation properties to calcification, and this assumption is examined in this work. Sliced mastectomy samples containing calcification were imaged at ×5 magnification using a digital specimen cabinet. Images of the individual calcifications were extracted, and the diameter and contrast of each calculated. The thicknesses of aluminium required to achieve the same contrast as each calcification when imaged under the same conditions were calculated using measurements of the contrast of aluminium foils. As hydroxyapatite and calcium oxalate are also used to simulate calcifications, the equivalent aluminium thicknesses of these materials were also calculated using tabulated attenuation coefficients. On average the equivalent aluminium thickness was 0.85 times the calcification diameter. For calcium oxalate and hydroxyapatite, the equivalent aluminium thicknesses were 1.01 and 2.19 times the thickness of these materials respectively. Aluminium and calcium oxalate are suitable substitute materials for calcifications. Hydroxyapatite is much more attenuating than the calcifications and aluminium. Using solid hydroxyapatite as a substitute for calcification of the same size would lead to excessive contrast in the mammographic image.

Microcalcifications in breast cancer: novel insights into the molecular mechanism and functional consequence of mammary mineralisation

BACKGROUND

Mammographic microcalcifications represent one of the most reliable features of nonpalpable breast cancer yet remain largely unexplored and poorly understood.

METHODS

We report a novel model to investigate the in vitro mineralisation potential of a panel of mammary cell lines. Primary mammary tumours were produced by implanting tumourigenic cells into the mammary fat pads of female BALB/c mice.

RESULTS

Hydroxyapatite (HA) was deposited only by the tumourigenic cell lines, indicating mineralisation potential may be associated with cell phenotype in this in vitro model. We propose a mechanism for mammary mineralisation, which suggests that the balance between enhancers and inhibitors of physiological mineralisation are disrupted. Inhibition of alkaline phosphatase and phosphate transport prevented mineralisation, demonstrating that mineralisation is an active cell-mediated process. Hydroxyapatite was found to enhance in vitro tumour cell migration, while calcium oxalate had no effect, highlighting potential consequences of calcium deposition. In addition, HA was also deposited in primary mammary tumours produced by implanting the tumourigenic cells into the mammary fat pads of female BALB/c mice.

CONCLUSION

This work indicates that formation of mammary HA is a cell-specific regulated process, which creates an osteomimetic niche potentially enhancing breast tumour progression. Our findings point to the cells mineralisation potential and the microenvironment regulating it, as a significant feature of breast tumour development.

Tissue refractive index as marker of disease

The gold standard in histopathology relies on manual investigation of stained tissue biopsies. A sensitive and quantitative method for in situ tissue specimen inspection is highly desirable, as it would allow early disease diagnosis and automatic screening. Here we demonstrate that quantitative phase imaging of entire unstained biopsies has the potential to fulfill this requirement. Our data indicates that the refractive index distribution of histopathology slides, which contains information about the molecular scale organization of tissue, reveals prostate tumors and breast calcifications. These optical maps report on subtle, nanoscale morphological properties of tissues and cells that cannot be recovered by common stains, including hematoxylin and eosin. We found that cancer progression significantly alters the tissue organization, as exhibited by consistently higher refractive index variance in prostate tumors versus normal regions. Furthermore, using the quantitative phase information, we obtained the spatially resolved scattering mean free path and anisotropy factor g for entire biopsies and demonstrated their direct correlation with tumor presence. In essence, our results show that the tissue refractive index reports on the nanoscale tissue architecture and, in principle, can be used as an intrinsic marker for cancer diagnosis.

Depth profiling of calcifications in breast tissue using picosecond Kerr-gated Raman spectroscopy

Breast calcifications are found in both benign and malignant lesions and their composition can indicate the disease state. Calcium oxalate (dihydrate) (COD) is associated with benign lesions, however calcium hydroxyapatite (HAP) is found mainly in proliferative lesions including carcinoma. The diagnostic practices of mammography and histopathology examine the morphology of the specimen. They can not reliably distinguish between the two types of calcification, which may indicate the presence of a cancerous lesion during mammography. We demonstrate for the first time that Kerr-gated Raman spectroscopy is capable of non-destructive probing of sufficient biochemical information from calcifications buried within tissue, and this information can potentially be used as a first step in identifying the type of lesion. The method uses a picosecond pulsed laser combined with fast temporal gating of Raman scattered light to enable spectra to be collected from a specific depth within scattering media by collecting signals emerging from the sample at a given time delay following the laser pulse. Spectra characteristic of both HAP and COD were obtained at depths of up to 0.96 mm, in both chicken breast and fatty tissue; and normal and cancerous human breast by utilising different time delays. This presents great potential for the use of Raman spectroscopy as an adjunct to mammography in the early diagnosis of breast cancer.

Mammography of ductal carcinoma in situ of the breast: review of 909 cases with radiographic-pathologic correlations

We retrospectively analysed mammographies of 909 ductal carcinoma in situ (DCIS) (1980-1999) and compared our results to those of literature. Microcalcifications were present in 75% of the cases, and soft-tissue abnormalities in 27% cases with association with calcifications in 14% of cases. Palpable masses were found in 12% of the cases and nipple discharge was present in 12% of the cases. The radiographic-pathologic correlation allowed to suspect the DCIS "aggressiveness" on radiologic signs. Granular, linear, branching and/or galactophoric topography of the microcalcifications were correlated with necrosis, grade 3, comedocarcinoma type. A number of microcalcifications higher than 20 was correlated with necrosis and grade 3. Mammographic size was correlated to histologic size. Masses were correlated with grade 1. A diagnosis strategy can be proposed with a multidisciplinar approach.

[Radiological diagnosis of mammary carcinomas. I: pathology and x-ray mammography]

Breast cancer is the most common malignant tumor in women: almost 10 % will suffer from breast cancer during their life and almost half of these will die of it. The spectrum of radiologic methods for diagnosing breast cancer is wide, including X-ray mammography, ultrasound, magnetic resonance mammography, and minimally invasive biopsies. After long-lasting controversies, breast cancer screening using X-ray mammography has now been introduced in Germany, following the projects in the Netherlands and Sweden. However, assessing mammographic films under screening conditions requires skills distinctly different from those needed under clinical conditions. This first part of two covers the histopathological basics and X-ray mammography; the second will deal with ultrasound of the breast and magnetic resonance mammography.

Atypical cystic lobule of the breast: an early stage of low-grade ductal carcinoma in-situ

The authors describe the characteristics of atypical cystic lobules (ACLs), which represent a step in the formation of low-grade ductal carcinoma in-situ. The authors define ACLs as a proliferation of luminal cells showing low-grade cytological atypia without architectural atypia. ACLs were compared with conventional hyperplasia, low-grade ductal carcinoma in-situ, and lobular neoplasia. 1) In about 40% of the cases, atypical cystic lobules merged with fully established micropapillary/cribriform ductal carcinoma in-situ. 2) Immunohistochemical staining for hormone receptors, keratin nineteen, and cyclin D1 revealed that atypical cystic lobules demonstrate a consistent immunophenotype, which differs from that of normal lobules and benign lesions and matches the one of low-grade ductal carcinoma in-situ. 3) ACLs are sometimes calcified. Osteopontin-positive histiocytes infiltrated all Kossa-positive (type II microcalcification) cribriform and comedo-type carcinomas and ACLs. The similarities in cytological and immunohistochemical features, the close proximity of the two types of proliferation, and the similarities with respect to calcification suggest that atypical cystic lobules represent an early stage in the formation of certain types of low-grade ductal carcinoma in-situ.

Role of high magnification specimen radiography in surgical and core biopsies of the breast

The clinical relevance of a high magnification specimen radiography (HMSR) system in breast biopsies was evaluated and compared with conventional specimen radiography with a mammography system (SRM). 100 surgical biopsies of 72 patients and 248 core biopsies of 30 patients were examined in (a) maximal 20-fold HMSR in combination with storage phosphors and (b) 1.8-fold SRM using a film-screen system. Detection of calcifications/soft tissue lesions and the impact on management were evaluated. In surgical biopsies, SRM could detect only 22% of individual microcalcifications, 39% of calcified lesions and 67% of soft tissue lesions identified with HMSR. Calcifications down to 10 microns were identified with HMSR. In five biopsies, peripheral calcifications leading to additional resection were recognized only with HMSR; in three of these they were indicative of malignant tissue. In core biopsies, only 12% of individual microcalcifications seen with HMSR were identified with SRM. 52% and 16% of all cores were calcified on HMSR and SRM, respectively. Microcalcifications within cores were found only with HMSR in 41% of patients with calcified lesions. In conclusion, the better detectability of microcalcifications with HMSR led to justified additional tissue resections in surgical patients and reduced the number of core biopsies required in interventional patients.

Detection of calcifications in breast biopsies by scanning electron microscopy

The identification of microcalcifications in breast biopsy specimens is a common and important task for the surgical pathologist that may sometimes be problematic. Although visualized by preoperative mammographic and operative specimen radiography, some cases may fail to reveal calcifications by histopathologic examination or occasion laborious and time-consuming study to confirm sparse calcifications. The present study demonstrates how conventional bright-field and polariscopic light microscopy did require considerable effort to confirm rare calcification. On the other hand, scanning electron microscopy was employed directly on a routine slide and provided definitive visual and physical proof, e.g., by means of energy dispersive x-ray microanalysis of a rare calcification on a slide previously judged to be negative for calcium and in a short period of time. Recent instrument advances in high voltage beam stabilization and in the ability to vary the pressure of the scanning electron microscope in the vicinity of the specimen now allow complete insertion of a diagnostic glass slide with only trivial preparation. The report, although brief, raises important questions regarding the extent and prevalence of breast calcifications.

Microcalcifications in ductal carcinoma in situ of the breast: histochemical and immunohistochemical study

Thirty cases of ductal carcinoma in situ (DCIS) of the breast, showing histological microcalcifications, were studied to clarify their mechanism of formation. Undecalcified sections revealed three types of calcium precipitates: type I and II granular calcifications (GCs) and laminar calcifications (LCs). In type I GCs the core on which the calcium had deposited was constituted mainly by nuclear debris. Type II GCs were predominantly composed by mucosubstances. LCs were the result of calcium deposits on mucoid or proteinaceous material, arranged in concentric lamellae. LCs and type II GCs were mainly present in well and intermediately differentiated DCIS. Type I GCs were observed in only DCIS with necrosis, frequently being present in intermediately and poorly differentiated DCIS.

Calcium oxalate crystals in benign breast cyst fluid

We have recently observed a strongly birefringent material of varying shapes and sizes in a benign breast cyst fluid specimen from a 52-yr-old woman with suspicious mammographic microcalcifications. The finding of calcium oxalate crystals in the breast cyst fluid should be regarded as a recognition of a particular type of calcification, easily overlooked with the conventional light microscopy. To date, we are unaware of any cytologic reports of this type of calcification in the breast.

Pathological assessment of nonpalpable breast lesions

Effective pathological examination of breast specimens from patients with nonpalpable radiologically detected lesions requires close cooperation among the pathologist, surgeon, and radiologist. Whenever possible, excision of the lesion should be documented by specimen radiography of the intact excisional biopsy. Diagnosis of the lesion and evaluation of margins should be based on permanent paraffin sections. Frozen section examination is not recommended routinely but may be employed in exceptional circumstances. Thermal damage to the tissue caused by electrocautery scalpels can reduce hormone receptor levels and can interfere with histological diagnosis.

Laboratory handling of impalpable breast lesions: a review

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