Breast imaging with positron emission tomography and fluorine-18 fluorodeoxyglucose: use and limitations

Hormonal Receptor Immunochemistry Heterogeneity and 18F-FDG Metabolic Heterogeneity: Preliminary Results of Their Relationship and Prognostic Value in Luminal Non-Metastatic Breast Cancers

Introduction

We aimed to investigate whether ¹⁸F-FDG PET metabolic heterogeneity reflects the heterogeneity of estrogen receptor (ER) and progesterone receptor (PR) expressions within luminal non-metastatic breast tumors and if it could help in identifying patients with worst event-free survival (EFS).

Materials and methods

On 38 PET high-resolution breast bed positions, a single physician drew volumes of interest encompassing the breast tumors to extract SUV_max, histogram parameters and textural features. High-resolution immunochemistry (IHC) scans were analyzed to extract Haralick parameters and descriptors of the distribution shape. Correlation between IHC and PET parameters were explored using Spearman tests. Variables of interest to predict the EFS status at 8 years (EFS-8y) were sought by means of a random forest classification. EFS-8y analyses were then performed using univariable Kaplan-Meier analyses and Cox regression analysis. When appropriate, Mann-Whitney tests and Spearman correlations were used to explore the relationship between clinical data and tumoral PET heterogeneity variables.

Results

For ER expression, correlations were mainly observed with ¹⁸F-FDG histogram parameters, whereas for PR expression correlations were mainly observed with gray-level co-occurrence matrix (GLCM) parameters. The strongest correlations were observed between skewness__ER and uniformity__HISTO (ρ = −0.386, p = 0.017) and correlation__PR and entropy__GLCM (ρ = 0.540, p = 0.001), respectively. The median follow-up was 6.5 years and the 8y-EFS was 71.0%. Random forest classification found age, clinical stage, SUV_max, skewness__ER, kurtosis__ER, entropy__HISTO, and uniformity__HISTO to be variables of importance to predict the 8y-EFS. Univariable Kaplan-Meier survival analyses showed that skewness__ER was a predictor of 8y-EFS (66.7 ± 27.2 versus 19.1 ± 15.2, p = 0.018 with a cut-off value set to 0.163) whereas other IHC and PET parameters were not. On multivariable analysis including age, clinical stage and skewness__ER, none of the parameters were independent predictors. Indeed, skewness__ER was significantly higher in youngest patients (ρ = −0.351, p = 0.031) and in clinical stage III tumors (p = 0.023).

Conclusion

A heterogeneous distribution of ER within the tumor in IHC appeared as an EFS-8y prognosticator in luminal non-metastatic breast cancers. Interestingly, it appeared to be correlated with PET histogram parameters which could therefore become potential non-invasive prognosticator tools, provided these results are confirmed by further larger and prospective studies.

Practical consensus recommendations regarding role of mastectomy in metastatic breast cancer

Whether to recommend mastectomy in metastatic disease or not has been a matter of debate. Is local therapy, such as mastectomy, of any benefit in advanced breast cancer is the main question. This expert group used data from published literature, practical experience and opinion of a large group of academic oncologists to arrive at these practical consensus recommendations for the benefit of community oncologists.

Characterisation of MRI Indeterminate Breast Lesions Using Dedicated Breast PET and Prone FDG PET-CT in Patients with Breast Cancer—A Proof-of-Concept Study

Magnetic resonance imaging (MRI) in patients with breast cancer to assess extent of disease or multifocal disease can demonstrate indeterminate lesions requiring second-look ultrasound and ultrasound or MRI-guided biopsies. Prone positron emission tomography-computed tomography (PET-CT) is a dedicated acquisition performed with a breast-supporting device on a standard PET-CT scanner. The MAMmography with Molecular Imaging (MAMMI, Oncovision, Valencia, Spain) PET system (PET-MAMMI) is a true tomographic ring scanner for the breast. We investigated if PET-MAMMI and prone PET-CT were able to characterise these MRI- indeterminate lesions further. A total of 10 patients with breast cancer and indeterminate lesions on breast MRI were included. Patients underwent prone PET-MAMMI and prone PET-CT after injection of FDG subsequently on the same day. Patients then resumed their normal pathway, with the clinicians blinded to the results of the PET-MAMMI and prone PET-CT. Of the MRI-indeterminate lesions, eight were histopathologically proven to be malignant and two were benign. PET-MAMMI and prone PET-CT only were able to demonstrate increased FDG uptake in 1/8 and 0/8 of the MRI-indeterminate malignant lesions, respectively. Of the MRI-indeterminate benign lesions, both PET-MAMMI and prone PET-CT demonstrated avidity in 1/2 of these lesions. Our findings do not support the use of PET-MAMMI to characterise indeterminate breast MRI lesions requiring a second look ultrasound.

Progress and Future Trends in PET/CT and PET/MRI Molecular Imaging Approaches for Breast Cancer

Breast cancer is a major disease with high morbidity and mortality in women worldwide. Increased use of imaging biomarkers has been shown to add more information with clinical utility in the detection and evaluation of breast cancer. To date, numerous studies related to PET-based imaging in breast cancer have been published. Here, we review available studies on the clinical utility of different PET-based molecular imaging methods in breast cancer diagnosis, staging, distant-metastasis detection, therapeutic and prognostic prediction, and evaluation of therapeutic responses. For primary breast cancer, PET/MRI performed similarly to MRI but better than PET/CT. PET/CT and PET/MRI both have higher sensitivity than MRI in the detection of axillary and extra-axillary nodal metastases. For distant metastases, PET/CT has better performance in the detection of lung metastasis, while PET/MRI performs better in the liver and bone. Additionally, PET/CT is superior in terms of monitoring local recurrence. The progress in novel radiotracers and PET radiomics presents opportunities to reclassify tumors by combining their fine anatomical features with molecular characteristics and develop a beneficial pathway from bench to bedside to predict the treatment response and prognosis of breast cancer. However, further investigation is still needed before application of these modalities in clinical practice. In conclusion, PET-based imaging is not suitable for early-stage breast cancer, but it adds value in identifying regional nodal disease and distant metastases as an adjuvant to standard diagnostic imaging. Recent advances in imaging techniques would further widen the comprehensive and convergent applications of PET approaches in the clinical management of breast cancer.

Head-to-Head Evaluation of 18F-FES and 18F-FDG PET/CT in Metastatic Invasive Lobular Breast Cancer

Invasive lobular carcinoma (ILC) demonstrates lower conspicuity on ¹⁸F-FDG PET than the more common invasive ductal carcinoma. Other molecular imaging methods may be needed for evaluation of this malignancy. As ILC is nearly always (95%) estrogen receptor (ER)-positive, ER-targeting PET tracers such as 16α-¹⁸F-fluoroestradiol (¹⁸F-FES) may have value. We reviewed prospective trials at Memorial Sloan Kettering Cancer Center using ¹⁸F-FES PET/CT to evaluate metastatic ILC patients with synchronous ¹⁸F-FDG and ¹⁸F-FES PET/CT imaging, which allowed a head-to-head comparison of these 2 PET tracers. Methods: Six prospective clinical trials using ¹⁸F-FES PET/CT in patients with metastatic breast cancer were performed at Memorial Sloan Kettering Cancer Center from 2008 to 2019. These trials included 92 patients, of whom 14 (15%) were of ILC histology. Seven of 14 patients with ILC had ¹⁸F-FDG PET/CT performed within 5 wk of the research ¹⁸F-FES PET/CT and no intervening change in management. For these 7 patients, the ¹⁸F-FES and ¹⁸F-FDG PET/CT studies were analyzed to determine the total number of tracer-avid lesions, organ systems of involvement, and SUV_max of each organ system for both tracers. Results: In the 7 comparable pairs of scans, there were a total of 254 ¹⁸F-FES-avid lesions (SUV_max, 2.6-17.9) and 111 ¹⁸F-FDG-avid lesions (SUV_max, 3.3-9.9) suggestive of malignancy. For 5 of 7 (71%) ILC patients, ¹⁸F-FES PET/CT detected more metastatic lesions than ¹⁸F-FDG PET/CT. In the same 5 of 7 patients, the SUV_max of ¹⁸F-FES-avid lesions was greater than the SUV_max of ¹⁸F-FDG-avid lesions. One patient had ¹⁸F-FES-avid metastases with no corresponding ¹⁸F-FDG-avid metastases. There were no patients with ¹⁸F-FDG-avid distant metastases without ¹⁸F-FES-avid distant metastases, although in one patient liver metastases were evident on ¹⁸F-FDG but not on ¹⁸F-FES PET. Conclusion: ¹⁸F-FES PET/CT compared favorably with ¹⁸F-FDG PET/CT for detection of metastases in patients with metastatic ILC. Larger prospective trials of ¹⁸F-FES PET/CT in ILC should be considered to evaluate ER-targeted imaging for clinical value in patients with this histology of breast cancer.

Positron emission tomography/computed tomography using 2-deoxy-2-fluoro-18-fluoro-D-glucose peri-tumoral halo uptake layer method outperforms magnetic resonance imaging and ultrasound methods in tumor size measurement of breast cancer

As a non-invasive method, positron emission tomography (PET)/computed tomography (CT) using 2-deoxy-2-fluoro-18-fluoro-D-glucose (18F-FDG) is applied as a useful modality in the diagnosis of breast cancer. By evaluating glucose metabolism, this method can also be used in staging, restaging and post-therapeutic response evaluation. To evaluate the reliability of the ¹⁸F-FDG PET/CT-based peri-tumoral halo uptake layer (PHL) method for assessing tumor size, a total of 79 female patients with breast cancer who underwent ¹⁸F-FDG PET/CT, breast ultrasound and magnetic resonance imaging (MRI) evaluations were included in the present study. Upon examination by two independent nuclear medicine radiologists, tumor sizes were estimated by ¹⁸F-FDG PET/CT using margins defined as the inner line of the PHL. Pathological tumor sizes were evaluated on the direction of largest diameter indicated by previous imaging examination, which were also utilized as final standards. Statistical analysis of the results suggested that ¹⁸F-FDG PET/CT had a more linear correlation with pathology compared with breast ultrasound (r²=0.89 vs. 0.73) and MRI (r²=0.89 vs. 0.69) in terms of tumor size estimation, including a significantly lower bias in size difference relative to pathology. ¹⁸F-FDG PET/CT also exhibited improved performance compared with breast ultrasound and MRI in T stage assessment. These results indicated that the ¹⁸F-FDG PET/CT-based PHL method was superior to breast ultrasound and MRI, and that it provides sufficient reliability and high accuracy for measuring tumor size in patients with breast cancer.

Comparison of FDG-PET/CT for Cancer Detection in Populations With Different Risks of Underlying Malignancy

Background/Aim: Whole-body positron-emission tomography/computed tomography with the glucose analog 2-[ 18 F]fluoro-2-deoxy-D-glucose (FDG-PET/CT) has been used to screen examinees for underlying malignancy in many countries. The aim of this study was to compare the potential value of FDG-PET/CT application in asymptomatic individuals with those with suspected malignancy. Patients and Methods: A total of 9,408 examinees underwent whole-body FDG-PET/CT at our hospital from July 2006 to August 2013. Three thousand and seven hundred asymptomatic individuals and 848 individuals with laboratory and clinical/radiologicaI suspicion of malignancy who had undergone FDG-PET/CT for cancer screening were recruited. The final confirmation of cancer and outcomes were based on a pathological report and continuous follow-up. Results: Forty-five out of 3,700 asymptomatic individuals (1.2%) had proven malignancy, and 42 of them (93.3%) were found by FDG-PET/CT. Two hundred and twelve out of 848 with suspected malignancy (25%) had proven malignancy, and 196 of them (92.5%) were detected by FDG-PET/CT. Most of these cancers in asymptomatic individuals were clinically at an early stage. The discovery rate in asymptomatic individuals and those with suspected malignancy was 1.1% and 23.1%, respectively. The overall survival of patients with cancer diagnosed with PET/CT was higher than those with suspected malignancy (78.6% vs. 48.5%, p<0.001). Patients with a resectable lesion, early-stage disease, and lower maximal standardized uptake value had significantly better survival than those without. Conclusion: FDG-PET/CT is useful in the early diagnosis of cancer and thus might improve the survival rates of these patients. Considering the costs and risk of radiation exposure, it would be better used as a priority in patients with laboratory and clinical/radiologic suspicion of malignancy.

Lymph Node Imaging in Patients with Primary Breast Cancer: Concurrent Diagnostic Tools

The detection of lymph node metastasis affects the management of patients with primary breast cancer significantly in terms of staging, treatment, and prognosis. The main goal for the radiologist is to determine and detect the presence of metastatic disease in nonpalpable axillary lymph nodes with a positive predictive value that is high enough to initially select patients for upfront axillary lymph node dissection. Features that are suggestive of axillary adenopathy may be seen with different imaging modalities, but ultrasound is the method of choice for evaluating axillary lymph nodes and for performing image-guided lymph node interventions. This review aims to provide a comprehensive overview of the available imaging modalities for lymph node assessment in patients diagnosed with primary breast cancer. IMPLICATIONS FOR PRACTICE: The detection of lymph node metastasis affects the management of patients with primary breast cancer. The main goal for the radiologist is to detect lymph node metastasis in patients to allow for the selection of patients who should undergo upfront axillary lymph node dissection. Features that are suggestive of axillary adenopathy may be seen with mammography, computed tomography, and magnetic resonance imaging, but ultrasonography is the imaging modality of choice for evaluating axillary lymph nodes. A normal axillary lymph node is characterized by a reniform shape, a maximal cortical thickness of 3 mm without focal bulging, smooth margins, and, depending on size, a discernable central fatty hilum.

Preclinical Molecular Imaging for Precision Medicine in Breast Cancer Mouse Models

Precision and personalized medicine is gaining importance in modern clinical medicine, as it aims to improve diagnostic precision and to reduce consequent therapeutic failures. In this regard, prior to use in human trials, animal models can help evaluate novel imaging approaches and therapeutic strategies and can help discover new biomarkers. Breast cancer is the most common malignancy in women worldwide, accounting for 25% of cases of all cancers and is responsible for approximately 500,000 deaths per year. Thus, it is important to identify accurate biomarkers for precise stratification of affected patients and for early detection of responsiveness to the selected therapeutic protocol. This review aims to summarize the latest advancements in preclinical molecular imaging in breast cancer mouse models. Positron emission tomography (PET) imaging remains one of the most common preclinical techniques used to evaluate biomarker expression in vivo, whereas magnetic resonance imaging (MRI), particularly diffusion-weighted (DW) sequences, has been demonstrated as capable of distinguishing responders from nonresponders for both conventional and innovative chemo- and immune-therapies with high sensitivity and in a noninvasive manner. The ability to customize therapies is desirable, as this will enable early detection of diseases and tailoring of treatments to individual patient profiles. Animal models remain irreplaceable in the effort to understand the molecular mechanisms and patterns of oncologic diseases.

Metabolic and volume-based parameters of (18F)FDG PET/CT for primary mass and axillary lymph node metastasis in patients with invasive ductal carcinoma: a retrospective analysis in relation to molecular subtype, axillary lymph node metastasis and immunohistochemistry and inflammatory markers

OBJECTIVE

To evaluate metabolic and volume-based parameters of 18-Fluorodeoxyglucose positron emission tomography/computed tomography ((F)FDG PET/CT) for primary mass and axillary lymph node (ALN) metastasis in relation to molecular subtype, and immunohistochemistry and inflammatory markers in patients with invasive ductal carcinoma.

METHODS

A total of 129 patients (mean±SD age: 49.2±13.0 years) with invasive ductal breast cancer who had (F)FDG PET/CT imaging prior to chemotherapy or surgery were included in this single-center retrospective study. Data on patient age, molecular subtype, ALN metastasis status, inflammatory markers, immunohistochemistry markers and (F)FDG PET/CT imaging parameters for primary mass and ALN were recorded.

RESULTS

ALN metastasis was evident in 52.7% of patients and associated with significantly higher median diameter (P=0.027), MTV (P<0.001) and TLG (P<0.001). NLR was positively correlated with all primary mass (p ranged from 0.041 to 0.001) and ALN (P ranged from 0.026 to <0.001) PET parameters. PET parameters did not change with respect to molecular subtype or immunohistochemistry markers. Primary mass and ALN metastasis PET parameters showed significant positive correlations for TLG (r=0.274, P=0.001) and SUVmax (r=0.358, P<0.001).

CONCLUSION

In conclusion, our findings in a retrospective cohort of invasive ductal breast cancer patients revealed primary mass PET parameters to significantly differ with respect to ALN metastasis status and NLR levels, but not according to molecular subtype or immunohistochemistry markers. Accordingly, our findings highlight the value of acquisition of preoperative PET/CT imaging and role of both metabolic and volume-based parameters in predicting aggressiveness of the tumor as correlated with presence of ALN metastasis and high NLR.

A preliminary study to propose a diagnostic algorithm for PET/CT-detected incidental breast lesions: application of BI-RADS lexicon for US in combination with SUVmax

OBJECTIVES

To develop a diagnostic algorithm for positron emission tomography (PET)-detected incidental breast lesions using both breast imaging reporting and data system (BI-RADS) and maximum standardized uptake value (SUVmax) criteria.

METHODS

Fifty-six PET-detected incidental breast lesions from 51 patients, which were subsequently investigated by breast ultrasound within 1 month of the PET study, constituted the study cohort and they were finally verified by tissue diagnosis or a 2-year follow-up. Based on the maximum specificity with sensitivity > 60.0% and maximum sensitivity with specificity > 60.0%, two SUVmax cutoff values were calculated at 2 and 3.7. BI-RADS ≥ 4 was considered as highly suspicious for malignancy. The diagnostic accuracies were estimated for SUVmax levels above or below the cutoff points combined with the BI-RADS suspicion level.

RESULTS

Overall, 46 benign and 10 malignant lesions were studied. The diagnostic characteristics of SUVmax ≥ 2, SUVmax ≥ 3.7, and BI-RADS ≥ 4 were 80.0%, 60.0%, and 80.0% for sensitivity, 73.9%, 95.7%, and 92.7% for specificity, and 75.0%, 89.3%, and 90.2% for accuracy, respectively. When the SUVmax threshold was set at 2, combined with BI-RADS suspicion level, the sensitivity, specificity, and accuracy were 100.0%, 69.6%, and 75.0%, respectively. The results for SUVmax threshold set at 3.7 combined with BI-RADS were 90.0%, 91.3%, and 91.1% for the sensitivity, specificity, and accuracy, respectively. A diagnostic algorithm was accordingly generated.

CONCLUSION

The need for biopsy should be justified in low BI-RADS lesions presenting with high SUVmax at 3.7 or higher. The biopsy of patients with high B-IRADS and low SUVmax could be preserved.

KEY POINTS

• A diagnostic algorithm was developed for PET-detected incidental breast lesions using both BI-RADS and SUVmax criteria. • Diagnostic performance was calculated separately and conjunctively for SUVmax ≥ 2, SUVmax ≥ 3.7, and BI-RADS ≥ 4. • The need for biopsy can be justified in BI-RADS < 4 lesions with SUVmax ≥ 3.7. Lesions with BI-RADS < 4 and indeterminate SUVmax (2 < SUVmax < 3.7) benefit from a short-interval follow-up. BI-RADS < 4 lesions with SUVmax < 2 may confidently be scheduled for routine screening.

Dedicated Breast Gamma Camera Imaging and Breast PET: Current Status and Future Directions

Recent advances in nuclear medicine instrumentation have led to the emergence of improved molecular imaging techniques to image breast cancer: dedicated gamma cameras using γ-emitting ^99mTc-sestamibi and breast-specific PET cameras using ¹⁸F-fluorodeoxyglucose. This article focuses on the current role of such approaches in the clinical setting including diagnosis, assessing local extent of disease, monitoring response to therapy, and, for gamma camera imaging, possible supplemental screening in women with dense breasts. Barriers to clinical adoption and technologies and radiotracers under development are also discussed.

Amino Acid Metabolism as a Target for Breast Cancer Imaging

Amino acids are an alternate energy source to glucose, and amino acid metabolism is up-regulated in multiple malignancies, including breast cancers. Multiple amino acid radiotracers have been used to image breast cancer with unique strengths and weaknesses. ¹¹C-methionine uptake correlates with S-phase fraction in breast cancer and may be useful for evaluation of treatment response. Invasive lobular breast cancers may demonstrate greater ¹⁸F-fluciclovine avidity than ¹⁸F-fluorodeoxyglucose. Thus, different histologic subtypes of breast cancer may use diverse metabolic pathways and may be better imaged by different tracers.

Assessing 18F-FDG Uptake in the Sentinel Lymph Node in Breast Cancer

¹⁸F-FDG PET/CT has limited value in early breast cancer. Sentinel lymph node (SLN) biopsy is the current procedure of choice to search for small metastatic deposits in the axillary lymph nodes in early breast cancer. In this retrospective study, we reevaluated ¹⁸F-FDG PET/CT images after locating the SLN on PET/CT with the help of SLN SPECT/CT images and assessed ¹⁸F-FDG uptake, particularly in the SLN. Our goal was to understand if combined evaluation of ¹⁸F-FDG PET/CT and SLN SPECT/CT could be useful for detecting early lymph node metastasis in the axilla. Methods: ¹⁸F-FDG PET/CT images of newly diagnosed breast cancer patients who also had SLN scintigraphy (SPECT/CT) and biopsy results were analyzed to assess ¹⁸F-FDG uptake in the SLN. The SLN seen on SPECT/CT images was located on PET/CT images, and its metabolic activity was assessed both visually and semiquantitatively using SUV_max ¹⁸F-FDG PET results were compared with the histopathology result for the SLN. Results: Twenty patients among 130 met the inclusion criteria. SLN SPECT/CT images were helpful for locating the SLN on ¹⁸F-FDG PET/CT images in all 20 patients. Histopathologic analysis of the SLNs demonstrated metastasis in 7 patients and no metastasis in 13. There was mild (visible) ¹⁸F-FDG uptake in the SLN (SUV_max, 1.2-4.1; metastatic deposit size, 6-8 mm) in 6 of 7 patients with SLN metastasis (85.7%). There was no or only faint ¹⁸F-FDG uptake in the SLN (SUV_max < 1) in 9 of 13 patients with no SLN metastasis (69.2%). Receiver-operating-characteristic curve analysis indicated that the SUV_max cutoff for differentiating SLN-positive from -negative cases was 0.85 (sensitivity, 85.7%; specificity, 61.5%; area under the curve, 0.747; P < 0.05). Conclusion: Combined evaluation of ¹⁸F-FDG PET/CT and SPECT/CT images to assess ¹⁸F-FDG uptake, particularly in the SLN, is a new image analysis technique to detect early metastatic disease in the axillary lymph nodes in breast cancer. Although this technique does not currently seem feasible for use in routine practice, mainly because of the limitations of current PET/CT technology in detecting small tumors, it is an interesting image analysis technique to be aware of for possible future use.

Use of Breast-Specific PET Scanners and Comparison with MR Imaging

The goals of this article are to discuss the role of breast-specific PET imaging of women with breast cancer, compare the clinical performance of positron emission mammography (PEM) and MR imaging for current indications, and provide recommendations for when women should undergo PEM instead of breast MR imaging.

18F-FDG PET/CT for Systemic Staging of Newly Diagnosed Breast Cancer in Men

¹⁸F-FDG PET/CT has demonstrated substantial value in systemic staging of newly diagnosed breast cancer in women. However, it is not known whether breast cancer in male patients benefits similarly. This study assesses ¹⁸F-FDG PET/CT systemic staging in patients with newly diagnosed male breast cancer and determines detection rates for unsuspected distant metastases stratified by pre-PET/CT stage. Methods: In this Institutional Review Board-approved retrospective study, our Health Care Information System was screened for stage I-III male patients with breast cancer who underwent ¹⁸F-FDG PET/CT before systemic or radiation therapy from 2004 to 2017. Initial stage was determined by mammography, ultrasound, or surgery. ¹⁸F-FDG PET/CT was evaluated to identify unsuspected extraaxillary regional nodal and distant metastases, and a post-PET/CT stage was determined. Rates of upstaging to stage IV were determined for each initial stage. Results: During the 14-y period, 10,124 unique patients underwent ¹⁸F-FDG PET/CT for breast cancer at our institution. Of these, 106 patients were men, and 39 of these patients were imaged at initial staging and met the inclusion criteria. Median age was 62 y (range, 31-90 y), most had ductal carcinoma (95%), and most were estrogen receptor-positive (97%). In 7 of 39 patients (18%), ¹⁸F-FDG PET/CT identified previously unsuspected distant metastases, which increased patient stage to IV. This included 3 of 19 (16%) initial stage IIB patients and 4 of 12 (33%) initial stage III patients. ¹⁸F-FDG PET/CT also detected an unsuspected synchronous lymphoma in 1 patient. Conclusion: ¹⁸F-FDG PET/CT revealed previously unsuspected distant metastases in 16% of male patients with pre-PET/CT stage IIB breast cancer and 33% of those with stage III breast cancer. These rates are comparable to previously published upstaging rates in female patients. ¹⁸F-FDG PET/CT demonstrates value for systemic staging of male patients with breast cancer and should be considered for use in newly diagnosed patients, particularly those with stage IIB and III disease.

Chemical exchange saturation transfer MRI to assess cell death in breast cancer xenografts at 7T

Purpose

Detecting cell death and predicting tumor response early in a course of chemotherapy could help optimize treatment regimens and improve clinical outcomes. Chemical exchange saturation transfer (CEST) MRI was investigated in vivo to study properties that may be able to detect cancer death.

Results

Using a magnetization transfer ratio (MTR) cutoff of 0.12 at 1.8 ppm was able to differentiate between viable tumor and cell death regions. Comparison of MTR values at this frequency showed significant differences (p < 0.0001) between viable tumor and cell death regions, matching patterns seen on histology. Using this cutoff, the mean increase in cell death index (± standard error of the mean) after chemotherapy was 4 ± 4%, 10% ± 7%, 10 ± 8%, and 4 ± 9% at 4, 8, 12, and 24 h, respectively.

Conclusions

CEST MRI can detect cell death in MDA-231 xenografts but further work is needed to characterize the clinical applications of this finding. Maximum response to chemotherapy occurred at 8-12 h after chemotherapy injection in this in vivo tumor model.

Materials and Methods

Breast cancer xenografts (MDA-MB-231) were scanned using 7 T MRI before and after chemotherapy. As a measure of CEST effect at 0.5 µT saturation amplitude, MTR values at frequency offsets of 1.8 and -3.3 ppm were evaluated. CEST signals after chemotherapy treatment were compared to cell-death histopathology of tumors.

Molecular Classification of Breast Cancer

Breast cancer is a heterogeneous disease, observed traditionally by morphology and protein expression but, more recently with the advent of modern molecular technologies, at the genomic and transcriptomic level. This review describes the association between the different molecular subtypes with the histologic subtypes of breast cancer alongside some of their major genomic characteristics and illustrates how these subtypes may affect the appearance of tumors on imaging studies. The authors aim to show how molecular stratification can be used to augment traditional methods to improve our understanding of breast cancers and their clinical management.

Role of Fludeoxyglucose in Breast Cancer: Treatment Response

After an overview of the principles of fludeoxyglucose-PET/computed tomography (CT) in breast cancer, its advantages and limits to evaluate treatment response are discussed. The metabolic information is helpful for early assessment of the response to neoadjuvant chemotherapy and could be used to monitor treatment, especially in aggressive breast cancer subtypes. PET/CT is also a powerful method for early assessment of the treatment response in the metastatic setting. It allows evaluation of different sites of metastases in a single examination and detection of a heterogeneous response. However, to use PET/CT to assess responses, methodology for image acquisition and analysis needs standardization.

Deep learning beyond cats and dogs: recent advances in diagnosing breast cancer with deep neural networks

Deep learning has demonstrated tremendous revolutionary changes in the computing industry and its effects in radiology and imaging sciences have begun to dramatically change screening paradigms. Specifically, these advances have influenced the development of computer-aided detection and diagnosis (CAD) systems. These technologies have long been thought of as "second-opinion" tools for radiologists and clinicians. However, with significant improvements in deep neural networks, the diagnostic capabilities of learning algorithms are approaching levels of human expertise (radiologists, clinicians etc.), shifting the CAD paradigm from a "second opinion" tool to a more collaborative utility. This paper reviews recently developed CAD systems based on deep learning technologies for breast cancer diagnosis, explains their superiorities with respect to previously established systems, defines the methodologies behind the improved achievements including algorithmic developments, and describes remaining challenges in breast cancer screening and diagnosis. We also discuss possible future directions for new CAD models that continue to change as artificial intelligence algorithms evolve.

ACR Appropriateness Criteria® Monitoring Response to Neoadjuvant Systemic Therapy for Breast Cancer

Patients with locally advanced invasive breast cancers are often treated with neoadjuvant chemotherapy prior to definitive surgical intervention. The primary aims of this approach are to: 1) reduce tumor burden thereby permitting breast conservation rather than mastectomy; 2) promptly treat possible metastatic disease, whether or not it is detectable on preoperative staging; and 3) potentially tailor future chemotherapeutic decisions by monitoring in-vivo tumor response. Accurate radiological assessment permits optimal management and planning in this population. However, assessment of tumor size and response to treatment can vary depending on the modality used, the measurement technique (such as single longest diameter, 3-D measurements, or calculated tumor volume), and varied response of different tumor subtypes to neoadjuvant chemotherapy (such as concentric shrinkage or tumor fragmentation). As discussed in further detail, digital mammography, digital breast tomosynthesis, US and MRI represent the key modalities with potential to help guide patient management. The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision include an extensive analysis of current medical literature from peer reviewed journals and the application of well-established methodologies (RAND/UCLA Appropriateness Method and Grading of Recommendations Assessment, Development, and Evaluation or GRADE) to rate the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where evidence is lacking or equivocal, expert opinion may supplement the available evidence to recommend imaging or treatment.

Non-coding RNAs in the reprogramming of glucose metabolism in cancer

Proliferating cancer cells reprogram their metabolic circuitry to thrive in an environment deficient in nutrients and oxygen. Cancer cells exhibit a higher rate of glucose metabolism than normal somatic cells, which is achieved by switching from oxidative phosphorylation to aerobic glycolysis to meet the energy and metabolites demands of tumour progression. This phenomenon, which is known as the Warburg effect, has generated renewed interest in the process of glucose metabolism reprogramming in cancer cells. Several regulatory pathways along with glycolytic enzymes are responsible for the emergence of glycolytic dependence. Non-coding (nc)RNAs are a class of functional RNA molecules that are not translated into proteins but regulate target gene expression. NcRNAs have been shown to be involved in various biological processes, including glucose metabolism. In this review, we describe the regulatory role of ncRNAs-specifically, microRNAs and long ncRNAs-in the glycolytic switch and propose that ncRNA-based therapeutics can be used to inhibit the process of glucose metabolism reprogramming in cancer cells.

Evaluation of nipple aspirate fluid as a diagnostic tool for early detection of breast cancer

There has been tremendous progress in detection of breast cancer in postmenopausal women, resulting in two-thirds of women surviving more than 20 years after treatment. However, breast cancer remains the leading cause of cancer-related deaths in premenopausal women. Breast cancer is increasing in younger women due to changes in life-style as well as those at high risk as carriers of mutations in high-penetrance genes. Premenopausal women with breast cancer are more likely to be diagnosed with aggressive tumours and therefore have a lower survival rate. Mammography plays an important role in detecting breast cancer in postmenopausal women, but is considerably less sensitive in younger women. Imaging techniques, such as contrast-enhanced MRI improve sensitivity, but as with all imaging approaches, cannot differentiate between benign and malignant growths. Hence, current well-established detection methods are falling short of providing adequate safety, convenience, sensitivity and specificity for premenopausal women on a global level, necessitating the exploration of new methods. In order to detect and prevent the disease in high risk women as early as possible, methods that require more frequent monitoring need to be developed. The emergence of "omics" strategies over the last 20 years, enabling the characterisation and understanding of breast cancer at the molecular level, are providing the potential for long term, longitudinal monitoring of the disease. Tissue and serum biomarkers for breast cancer stratification, diagnosis and predictive outcome have emerged, but have not successfully translated into clinical screening for early detection of the disease. The use of breast-specific liquid biopsies, such as nipple aspirate fluid (NAF), a natural secretion produced by breast epithelial cells, can be collected non-invasively for biomarker profiling. As we move towards an age of active surveillance, home-based liquid biopsy collection kits are increasingly being applied and these could provide a paradigm shift where NAF biomarker profiling is used for routine breast health monitoring. The current status of established and newly emerging imaging techniques for early detection of breast cancer and the potential for alternative biomarker screening of liquid biopsies, particularly those applied to high-risk, premenopausal women, will be reviewed.

Ultrasound Imaging Technologies for Breast Cancer Detection and Management: A Review

Ultrasound imaging is a commonly used modality for breast cancer detection and diagnosis. In this review, we summarize ultrasound imaging technologies and their clinical applications for the management of breast cancer patients. The technologies include ultrasound elastography, contrast-enhanced ultrasound, 3-D ultrasound, automatic breast ultrasound and computer-aided detection of breast ultrasound. We summarize the study results seen in the literature and discuss their future directions. We also provide a review of ultrasound-guided, breast biopsy and the fusion of ultrasound with other imaging modalities, especially magnetic resonance imaging (MRI). For comparison, we also discuss the diagnostic performance of mammography, MRI, positron emission tomography and computed tomography for breast cancer diagnosis at the end of this review. New ultrasound imaging techniques, ultrasound-guided biopsy and the fusion of ultrasound with other modalities provide important tools for the management of breast patients.

Improved visualization of breast tissue on a dedicated breast PET system through ergonomic redesign of the imaging table

Background

Breast lesions closer than 2 cm to the chest wall are difficult to position in the field of view of dedicated breast PET (db-PET) systems. This inability to detect such lesions is a significant limitation of these systems. The primary objective of this study was to determine if modifications to the design of the imaging table and detector used for a db-PET system would enable improved visualization of breast tissue close to the chest wall. All studies were performed on a commercially available db-PET system (Mammi-PET). A central square section of the imaging table, containing the standard 180-mm circular aperture, was modified such that it could be removed and replaced by thinner sections with a larger aperture. Additional changes were made to the cover plate of the detector array and the patient mattress. A total of 60 patients were studied. After administration of F-18 FDG, 30 patients were imaged with a 220-mm-diameter aperture and the standard aperture, and 30 patients with a 200-mm aperture and the standard aperture. On all scans, the length of breast tissue in the field of view was measured as the greatest extent of tissue from the nipple back to the posterior edge of the breast. Image quality and patient comfort were recorded.

Results

Averaged over both breasts, relative to the standard aperture, the increase in breast length was 12.5 + 7.7 mm with the 220-mm aperture, and 12.3 + 6.5 mm with the 200-mm aperture (p < 0.05 for both apertures). In ~ 5% of cases, the larger apertures resulted in some degradation in image quality due to closer proximity to cardiac/hepatic activity. In 10–20% of cases, movement of the breast tissue was observed as the detector ring was moved to scan the anterior region of the breast. The patient survey indicated no significant difference in the comfort level between the standard aperture and either of the prototype apertures.

Conclusions

Modifications to the image table and system resulted in a significant gain in the volume of breast tissue that could be imaged on the db-PET system and should allow better visualization of lesions close to the chest wall.

FDG avid breast cancer bone metastases silent on CT and scintigraphy: a case report with radiologic-pathologic correlation

Bone is the one of the most common distant metastatic sites in breast cancer. Routine initial breast cancer staging evaluation typically includes computed tomography (CT) and skeletal scintigraphy while 18F fluorodeoxyglucose (FDG) positron emission tomography-computed tomography (PET-CT) is reserved for clinically high-risk cases. Since FDG PET-CT is not routinely performed during staging or surveillance evaluations, it is important for radiologists and clinicians to appreciate the limitations of bone metastasis detection on CT and scintigraphy. We present a case of bony metastases of invasive ductal carcinoma of the breast which were not detected on diagnostic CT or skeletal scintigraphy but were metabolically active on FDG PET-CT and evident on magnetic resonance. We provide a review of the literature and radiologic–pathologic correlation to explain the discordant imaging findings.

Bone metastases from breast cancer: associations between morphologic CT patterns and glycolytic activity on PET and bone scintigraphy as well as explorative search for influential factors

Background

This study aimed to compare the detection of bone metastases from breast cancer on F-18 fluorodeoxyglucose positron emission tomography (FDG-PET) and bone scintigraphy (BS). An explorative search for factors influencing the sensitivity or uptake of BS and FDG-PET was also performed.

Methods

Eighty-eight patients with bone metastases from breast cancer were eligible for this study. Histological confirmation of bone metastases was obtained in 31 patients. The bone metastases were visually classified into four types based on their computed tomography (CT) appearance: osteoblastic, osteolytic, mixed, and negative. The sensitivity of BS and FDG-PET were obtained regarding CT type, adjuvant therapy, and the primary tumor characteristics. The FDG maximum standardized uptake value (SUV_max) was analyzed.

Results

The sensitivities of the three modalities (CT, BS, and FDG-PET) were 77, 89, and 94%, respectively. The sensitivity of FDG-PET for the osteoblastic type (69%) was significantly lower than that for the other types (P < 0.001), and the sensitivity of BS for the negative type (70%) was significantly lower than that for the others. Regarding tumor characteristics, the sensitivity of FDG-PET significantly differed between nuclear grade (NG)1 and NG2–3 (P = 0.032). The SUV_max of the osteoblastic type was significantly lower than that of the other types (P = 0.009). The SUV_max of NG1 was also significantly lower than that of NG2–3 (P = 0.011). No significant difference in FDG uptake (SUV_max) was detected between different histological types.

Conclusion

Although FDG-PET is superior to BS for the detection of bone metastases from breast cancer, this technique has limitations in depicting osteoblastic bone metastases and NG1.

Incremental Value of Cocktail 18F-FDG and 18F-NaF PET/CT Over 18F-FDG PET/CT Alone for Characterization of Skeletal Metastases in Breast Cancer

PURPOSE

The aim of this study was to evaluate the incremental value of cocktail F-FDG/F-NaF PET/CT over F-FDG PET/CT alone for detection of skeletal metastases in breast cancer patients.

METHODS

Seventy patients with locally advanced/recurrent breast cancer were prospectively included. All patients underwent whole-body F-FDG PET/CT and cocktail F-FDG/F-NaF PET/CT within a span of 1 week. Both studies were evaluated to detect presence of skeletal/marrow metastases on PET/CT images by 2 nuclear medicine physicians. Clinical and radiological correlation/follow-up was used as criterion standard.

RESULTS

Of 70 patients, 50 (71.0%) had locally advanced breast cancer, and 20 had recurrent breast cancer. On patient-wise analysis, both cocktail PET/CT and F-FDG PET/CT identified skeletal/marrow lesions in 23 (32.8%) of 70 patients. In 8 patients (11.4%), only cocktail PET/CT identified skeletal/marrow lesions, whereas F-FDG PET/CT was negative. In the rest of the 39 patients (55.8%), no skeletal/marrow lesion was identified on both scans. Good correlation was noted between cocktail PET/CT and F-FDG PET/CT results (r = 0.785, P < 0.0001). Cocktail PET/CT detected lesions in significantly more number of patients than F-FDG PET/CT alone (P = 0.007). On lesion-wise analysis, cocktail PET/CT detected more number of lesions in 20 patients as compared with F-FDG-PET/CT alone. Both scans detected same number of lesions in the rest of 11 patients with positive findings. A total of 32 additional lesions were identified on cocktail PET/CT imaging as compared with F PET/CT alone (P < 0.0001).

CONCLUSIONS

Cocktail F-FDG and F-NaF PET/CT is superior to F-FDG PET/CT alone for the detection of skeletal/marrow metastases in breast cancer. It can be a better alternative to F-FDG PET/CT alone in facilities where both tracers are available.

PET/MRI of the breast

The future clinical use of the combination of positron emission tomography (PET) with 2-Fluoro[F-18]-2-Deoxy-d-Glucose (FDG)and MRI is still unclear. If a patient requires a PET and breast DCE-MRI for staging purposes, both scans can be done in the same visit. In the breast, DCE-MRI is better at lesion detection (sensitivity), margin evaluation, and has a higher specificity than CT. The potential for multiparametric qualitative and quantitative imaging is also an advantage of PET/MRI which provides opportunity to improve tumor characterization and may ultimately lead to outcome prediction. This review discusses technical and clinical aspects of this emerging technology in breast cancer patients.

Strong association of epidermal growth factor receptor status with breast cancer FDG uptake

PURPOSE

Imaging tumor FDG uptake could complement breast cancer biomarkers of risk and treatment response. Although breast cancer FDG uptake is reputedly influenced by major biomarker states, the role of epidermal growth factor receptor (EGFR) expression remains largely unexplored.

METHODS

This is a retrospective study that included 499 patients with primary breast cancer at initial presentation. Tumor FDG uptake was measured on pretreatment PET/CT as maximum standardized uptake value (SUVmax), and biomarkers were assessed by immunohistochemistry of tumor tissue. Regression analysis was performed for predictors of high tumor FDG uptake (SUVmax ≥ 8.6).

RESULTS

SUVmax was higher in ER- (36.5%; 11.2 ± 6.0 vs. 8.3 ± 5.3), PR- (42.3%; 10.9 ± 6.0 vs. 8.2 ± 5.2), and triple-negative tumors (19.8%; 12.0 ± 6.9 vs. 8.7 ± 5.2; all p < 0.0001). EGFR expression (28.5%) was more frequent in ER-, PR-, triple-negative, cytokeratin 5/6 (CK5/6) + and mutant P53 (mP53) + tumors (all p < 0.0001). EGFR+ was associated with higher SUVmax among all tumors (11.9 ± 6.0 vs. 8.3 ± 5.3), ER- tumors (p < 0.0001), PR- and + tumors (p < 0.0001 and 0.027), hormone receptor- and + tumors (p < 0.0001 and 0.004), human epidermal growth factor receptor 2 (HER2)- and + tumors (p < 0.0001 and 0.006), non-triple negative tumors (p < 0.0001), CK5/6- and + tumors (p = 0.021 and <0.0001), and mP53- and + tumors (p < 0.0001 and 0.008). Tumors had high FDG uptake in 73.2% of EGFR+ and 40.6% of EGFR- tumors. On regression analysis, significant multivariate predictors of high tumor FDG uptake were large size, EGFR+ and CK5/6+ for the entire subjects, and EGFR+ and CK5/6+ for ER- and hormone receptor negative subgroups. High FDG uptake was able to sub-stratify EGFR+ tumors that were more likely to be ER- and CK5/6+, and EGFR- tumors more likely to be mP53 +.

CONCLUSIONS

Primary breast tumor FDG uptake is strongly influenced by EGFR status beyond that by other major biomarkers including hormone receptor and HER2 status, and EGFR expression is a strong independent predictor of high breast tumor FDG uptake.

A Case of Adenomyoepithelioma of the Breast Showing Strong Uptake of 18 F-Fluorodeoxyglucose on a Positron Emission Tomography

An adenomyoepithelioma of the breast is a rare tumor characterized by biphasic proliferation of both epithelial and myoepithelial cells. This tumor is generally considered as a benign neoplasm, and there are few reports describing the imaging features of this tumor through ¹⁸ F-fluorodeoxyglucose positron emission tomography (FDG-PET). Here, we report a case of an adenomyoepithelioma that showed strong uptake of FDG on PET similar to that observed with a malignant tumor. A 73-year-old woman presented to our hospital with a 3.5-cm, mobile, and elastic hard tumor in the upper area of the left breast. Although the findings of mammography, ultrasonography, and contrast-enhanced magnetic resonance imaging suggested that the tumor was malignant, it was diagnosed as an adenomyoepithelioma by core needle biopsy. An invasive ductal carcinoma, 0.5-cm in size, was detected in the medial upper area of the ipsilateral breast during an examination. Although FDG-PET demonstrated no lymph node or distant metastases from the invasive ductal carcinoma, strong uptake of FDG was detected in the adenomyoepithelioma. Breast conserving surgery and sentinel lymph node biopsy for the invasive ductal carcinoma together with resection of the adenomyoepithelioma was performed. A diagnosis of adenomyoepithelioma was confirmed through histologic examination of the resected specimen. This case indicates that some adenomyoepitheliomas may show a strong uptake of FDG on PET, which resembles a malignant tumor.

Higher breast cancer conspicuity on dbPET compared to WB-PET/CT

OBJECTIVES

The purpose of this study was to evaluate lesion detectability of a dedicated breast positron-emission tomography (dbPET) scanner for breast cancers with an updated reconstruction mode, comparing it to whole-body positron-emission tomography/computed tomography (WB-PET/CT).

MATERIALS AND METHODS

A total of 179 histologically-proven breast cancer lesions in 150 females who underwent both WB-PET/CT and dbPET with ¹⁸F-fluorodeoxyglucose were retrospectively analyzed. The patient/breast/lesion-based sensitivities based on visual analysis were compared between dbPET and WB-PET/CT. For lesions visible on both PET images, SUVmax values of the tumors were measured, and tumor-to-background ratios (T/B ratios) of SUVmax were compared between the two scans. Subgroup analyses according to clinical tumor stage, histopathology and histological grade were also performed.

RESULTS

Patient/breast/lesion-based sensitivities were 95%, 95%, and 92%, respectively, for dbPET, and 95%, 94%, and 88%, respectively, for WB-PET/CT. Mean±standard deviation SUVmax values of FDG-avid tumors were 13.0±9.7 on dbPET and 6.4±4.8 on WB-PET. T/B ratios were also significantly higher in dbPET than in WB-PET/CT (8.1±7.1 vs. 5.1±4.5). In the subgroup analysis, no significant differences in sensitivities between dbPET and WB-PET/CT were found. However, T/B ratios of dbPET were significantly higher than those of WB-PET/CT in cT1c, cT2, cT3, invasive cancer, invasive carcinoma of no special type, mucinous carcinoma and Grades 1-3.

CONCLUSION

No significant differences in sensitivities were identified between dbPET using an updated reconstruction mode and WB-PET/CT; however, T/B ratios of dbPET were significantly higher than those of WB-PET/CT, indicating higher tumor conspicuity on dbPET.

Clinical PET-MR Imaging in Breast Cancer and Lung Cancer

Hybrid imaging systems have dramatically improved thoracic oncology patient care over the past 2 decades. PET-MR imaging systems have the potential to further improve imaging of thoracic neoplasms, resulting in diagnostic and therapeutic advantages compared with current MR imaging and PET-computed tomography systems. Increasing soft tissue contrast and lesion sensitivity, improved image registration, reduced radiation exposure, and improved patient convenience are immediate clinical advantages. Multiparametric quantitative imaging capabilities of PET-MR imaging have the potential to improve understanding of the molecular mechanisms of cancer and treatment effects, potentially guiding improvements in diagnosis and therapy.

Performance evaluation of a high resolution dedicated breast PET scanner

PURPOSE

Early stage breast cancers may not be visible on a whole-body PET scan. To overcome whole-body PET limitations, several dedicated breast positron emission tomography (DbPET) systems have emerged nowadays aiming to improve spatial resolution. In this work the authors evaluate the performance of a high resolution dedicated breast PET scanner (Mammi-PET, Oncovision).

METHODS

Global status, uniformity, sensitivity, energy, and spatial resolution were measured. Spheres of different sizes (2.5, 4, 5, and 6 mm diameter) and various 18 fluorodeoxyglucose ((18)F-FDG) activity concentrations were randomly inserted in a gelatine breast phantom developed at our institution. Several lesion-to-background ratios (LBR) were simulated, 5:1, 10:1, 20:1, 30:1, and 50:1. Images were reconstructed using different voxel sizes. The ability of experienced reporters to detect spheres was tested as a function of acquisition time, LBR, sphere size, and matrix reconstruction voxel size. For comparison, phantoms were scanned in the DbPET camera and in a whole body PET (WB-PET). Two patients who just underwent WB-PET/CT exams were imaged with the DbPET system and the images were compared.

RESULTS

The measured absolute peak sensitivity was 2.0%. The energy resolution was 24.0% ± 1%. The integral and differential uniformity were 10% and 6% in the total field of view (FOV) and 9% and 5% in the central FOV, respectively. The measured spatial resolution was 2.0, 1.9, and 1.7 mm in the radial, tangential, and axial directions. The system exhibited very good detectability for spheres ≥4 mm and LBR ≥10 with a sphere detection of 100% when acquisition time was set >3 min/bed. For LBR = 5 and acquisition time of 7 min the detectability was 100% for spheres of 6 mm and 75% for spheres of 5, 4, and 2.5 mm. Lesion WB-PET detectability was only comparable to the DbPET camera for lesion sizes ≥5 mm when acquisition time was >3 min and LBR > 10.

CONCLUSIONS

The DbPET has a good performance for its clinical use and shows an improved resolution and lesion detectability of small lesions compared to WB-PET.

Breast PET/MR Imaging

Breast and whole-body PET/MR imaging is being used to detect local and metastatic disease and is being investigated for potential imaging biomarkers, which may eventually help personalize treatments and prognoses. This article provides an overview of breast and whole-body PET/MR exam techniques, summarizes PET and MR breast imaging for lesion detection, outlines investigations into multi-parametric breast PET/MR, looks at breast PET/MR in the setting of neo-adjuvant chemotherapy, and reviews the pros and cons of whole-body PET/MR in the setting of metastatic or suspected metastatic breast cancer.

Spectrum of the Breast Lesions With Increased 18F-FDG Uptake on PET/CT

Interpretation of ¹⁸F-FDG PET/CT studies in breast is challenging owing to nonspecific FDG uptake in various benign and malignant conditions. Benign conditions include breast changes in pregnancy and lactation, gynecomastia, mastitis, fat necrosis, fibroadenoma, intraductal papilloma, and atypical ductal hyperplasia. Among malignancies, invasive ductal carcinoma and invasive lobular carcinoma are common histological types of breast carcinoma. Rarely, other unusual histological types of breast carcinomas (eg, intraductal papillary carcinoma, invasive micropapillary carcinoma, medullary carcinoma, mucinous carcinoma, and metaplastic carcinoma), lymphoma, and metastasis can be the causes. Knowledge of a wide spectrum of hypermetabolic breast lesions on FDG PET/CT is essential in accurate reading of FDG PET/CT. The purpose of this atlas article is to demonstrate features of various breast lesions encountered at our institution, both benign and malignant, which can result in hypermetabolism on FDG PET/CT imaging.