Axillary Lymphadenopathy After a COVID-19 Vaccine Booster Dose: Time to Resolution on Ultrasound Follow-Up and Associated Factors

Background: Given ongoing administration of booster doses of COVID-19 vaccines, radiologists are continuing to encounter COVID-19 vaccine-related axillary lymphadenopathy on imaging. Objective: The purpose of this study was to assess the time to resolution of COVID-19 vaccine-related axillary lymphadenopathy identified on breast ultrasound after a booster dose, and to assess factors potentially associated with the time to resolution. Methods: This retrospective single-institution study included 54 patients (mean age, 57 years) with unilateral axillary lymphadenopathy ipsilateral to a booster dose of mRNA COVID-19 vaccine visualized on ultrasound (whether an initial breast imaging examination or follow-up to prior screening or diagnostic breast imaging) performed between September 1st, 2021, and December 31st, 2022, and who underwent follow-up ultrasound examinations until resolution of lymphadenopathy. Patient information was extracted from the EMR. Univariable and multivariable linear regression analyses were used to identify predictors of time to resolution. Time to resolution was compared with a previously published sample of 64 patients from the study institution that was used to evaluate the time to resolution of axillary lymphadenopathy after the initial vaccine series. Results: A total of 6/54 patients had a history of breast cancer; 2/54 patients had symptoms related to the axillary lymphadenopathy (axillary pain in both patients). The initial ultrasound examinations showing the lymphadenopathy comprised 33/54 screening ultrasound examinations and 21/54 diagnostic ultrasound examinations. The lymphadenopathy resolved a mean of 102±56 days after the booster dose and 84±49 days after the initial ultrasound showing the lymphadenopathy. Age, vaccine booster type (Moderna vs Pfizer), and history of breast cancer were not significantly associated with time to resolution in univariable or multivariable analyses (all p>.05). Time to resolution after a booster dose was significantly shorter than the time to resolution after the first dose of the initial series (mean, 129±37 days) (p=.01). Conclusion: Axillary lymphadenopathy after a COVID-19 vaccine booster dose has a mean time to resolution of 102 days, shorter than the time to resolution after the initial series. Clinical Impact: The time to resolution after a booster dose supports the current recommendation for a follow-up interval of at least 12 weeks for suspected vaccine-related lymphadenopathy.

Radiologic and Pathologic Correlation for Angiolipomas of the Breast

Angiolipomas of the breast are rare; however, they are an important entity for the radiologist who determines radiologic-pathologic concordance and recommends appropriate management. They can present as a palpable concern, prompting diagnostic workup, or can be detected on screening breast examinations. They often present as a circumscribed low-density mass on mammography, which is hyperechoic on sonography; associated fibrin thrombi can produce soft tissue density and/or hypoechoic foci that appear hypointense on T1-weighted MRI. Due to the nonspecific radiographic appearance, tissue sampling is often required for definitive diagnosis. Pathologically, angiolipomas can be difficult to distinguish from angiosarcomas; however, scattered microthrombi in small blood vessels are a typical feature of angiolipomas. Generally, in the setting of radiologic-pathologic concordance, angiolipomas do not need to be excised and can be followed clinically when palpable. Surgical excision can be pursued when certain high-risk features, such as nuclear enlargement, an infiltrative pattern, endothelial mitoses, and a high proliferation rate, are present in the core-needle biopsy specimen.

Breast Cancer Disparities Through the Lens of the COVID-19 Pandemic

Purpose of Review

The emergency medicine and critical care needs of the COVID-19 pandemic forced a sudden and dramatic disruption of cancer screening and treatment programs in the USA during the winter and spring of 2020. This review commentary addresses the impact of the pandemic on racial/ethnic minorities such as African Americans and Hispanic-Latina Americans, with a focus on factors related to breast cancer.

Recent Findings

African Americans and Hispanic-Latina Americans experienced disproportionately higher morbidity and mortality from COVID-19; many of the same socioeconomic and tumor biology/genetic factors that explain breast cancer disparities are likely to account for COVID-19 outcome disparities.

Summary

The breast cancer clinical and research community should partner with public health experts to ensure participation of diverse patients in COVID-19 treatment trials and vaccine programs and to overcome COVID-19-related breast health management delays that are likely to have been magnified among African Americans and Hispanic-Latina Americans.

Merkel cell carcinoma of the breast: A case report

Merkel cell carcinoma (MCC) of the breast is a very rare and aggressive type of neuroendocrine carcinoma of the breast (NECB) that typically occurs in older and immunocompromised individuals often presenting as a large palpable mass (Albright et al., 2018¹). Imaging features of MCC are similar to other NECBs, typically appearing as an oval circumscribed mass on mammography and as an irregular mass with increased vascularity on sonography (Jeon et al., 2014²). While both MCC and primary NECB demonstrate positive immunostaining for synaptophysin, obtaining immunohistochemical stains for specific markers, such as CK7 and CK20 is imperative to confirm the diagnosis of MCC (Albright et al., 2018¹). We present a case of a 57-year-old female patient with no personal or family history of breast cancer, who presented for evaluation of a palpable abnormality in her left breast. Initial diagnostic mammogram demonstrated a circumscribed mass in the upper outer quadrant of the left breast corresponding to the palpable area of concern, which correlated to an irregular mass with increased vascularity on targeted ultrasound, similar to other NECBs. Pathologic results after tissue sampling yielded poorly differentiated primary NECB. Following neoadjuvant chemotherapy, the patient underwent a lumpectomy and further immunohistochemical stains of the lumpectomy specimen demonstrated diffusely positive synaptophysin, negative CK7, and positive CK20, consistent with MCC of the breast.

Dielectrowetting of a thin nematic liquid crystal layer

We consider a mathematical model that describes the flow of a nematic liquid crystal (NLC) film placed on a flat substrate, across which a spatially varying electric potential is applied. Due to their polar nature, NLC molecules interact with the (nonuniform) electric field generated, leading to instability of a flat film. Implementation of the long wave scaling leads to a partial differential equation that predicts the subsequent time evolution of the thin film. This equation is coupled to a boundary value problem that describes the interaction between the local molecular orientation of the NLC (the director field) and the electric potential. We investigate numerically the behavior of an initially flat film for a range of film heights and surface anchoring conditions.

Integrated Multi-Tumor Radio-Genomic Marker of Outcomes in Patients with High Serous Ovarian Carcinoma

Purpose: Develop an integrated intra-site and inter-site radiomics-clinical-genomic marker of high grade serous ovarian cancer (HGSOC) outcomes and explore the biological basis of radiomics with respect to molecular signaling pathways and the tumor microenvironment (TME). Method: Seventy-five stage III-IV HGSOC patients from internal (N = 40) and external factors via the Cancer Imaging Archive (TCGA) (N = 35) with pre-operative contrast enhanced CT, attempted primary cytoreduction, at least two disease sites, and molecular analysis performed within TCGA were retrospectively analyzed. An intra-site and inter-site radiomics (cluDiss) measure was combined with clinical-genomic variables (iRCG) and compared against conventional (volume and number of sites) and average radiomics (N = 75) for prognosticating progression-free survival (PFS) and platinum resistance. Correlation with molecular signaling and TME derived using a single sample gene set enrichment that was measured. Results: The iRCG model had the best platinum resistance classification accuracy (AUROC of 0.78 [95% CI 0.77 to 0.80]). CluDiss was associated with PFS (HR 1.03 [95% CI: 1.01 to 1.05], p = 0.002), negatively correlated with Wnt signaling, and positively to immune TME. Conclusions: CluDiss and the iRCG prognosticated HGSOC outcomes better than conventional and average radiomic measures and could better stratify patient outcomes if validated on larger multi-center trials.

Extranodal multifocal Rosai-Dorfman disease of the breast: A case report

We report a case of a 49-year-old female diagnosed with extranodal multifocal Rosai-Dorfman disease (RDD) of the breast using mammography and ultrasound. RDD is a rare non-Langerhans cell benign proliferative disorder of histiocytes that usually involves the lymph nodes, but may involve extranodal sites. We review the clinical presentation as well as imaging features of this rare disease on multiple modalities and the importance of recognizing the diagnosis in order to direct treatment.

Fully Automated Convolutional Neural Network Method for Quantification of Breast MRI Fibroglandular Tissue and Background Parenchymal Enhancement

The aim of this study is to develop a fully automated convolutional neural network (CNN) method for quantification of breast MRI fibroglandular tissue (FGT) and background parenchymal enhancement (BPE). An institutional review board-approved retrospective study evaluated 1114 breast volumes in 137 patients using T1 precontrast, T1 postcontrast, and T1 subtraction images. First, using our previously published method of quantification, we manually segmented and calculated the amount of FGT and BPE to establish ground truth parameters. Then, a novel 3D CNN modified from the standard 2D U-Net architecture was developed and implemented for voxel-wise prediction whole breast and FGT margins. In the collapsing arm of the network, a series of 3D convolutional filters of size 3 × 3 × 3 are applied for standard CNN hierarchical feature extraction. To reduce feature map dimensionality, a 3 × 3 × 3 convolutional filter with stride 2 in all directions is applied; a total of 4 such operations are used. In the expanding arm of the network, a series of convolutional transpose filters of size 3 × 3 × 3 are used to up-sample each intermediate layer. To synthesize features at multiple resolutions, connections are introduced between the collapsing and expanding arms of the network. L2 regularization was implemented to prevent over-fitting. Cases were separated into training (80%) and test sets (20%). Fivefold cross-validation was performed. Software code was written in Python using the TensorFlow module on a Linux workstation with NVIDIA GTX Titan X GPU. In the test set, the fully automated CNN method for quantifying the amount of FGT yielded accuracy of 0.813 (cross-validation Dice score coefficient) and Pearson correlation of 0.975. For quantifying the amount of BPE, the CNN method yielded accuracy of 0.829 and Pearson correlation of 0.955. Our CNN network was able to quantify FGT and BPE within an average of 0.42 s per MRI case. A fully automated CNN method can be utilized to quantify MRI FGT and BPE. Larger dataset will likely improve our model.

Deep Neural Networks Improve Radiologists' Performance in Breast Cancer Screening

We present a deep convolutional neural network for breast cancer screening exam classification, trained, and evaluated on over 200000 exams (over 1000000 images). Our network achieves an AUC of 0.895 in predicting the presence of cancer in the breast, when tested on the screening population. We attribute the high accuracy to a few technical advances. 1) Our network's novel two-stage architecture and training procedure, which allows us to use a high-capacity patch-level network to learn from pixel-level labels alongside a network learning from macroscopic breast-level labels. 2) A custom ResNet-based network used as a building block of our model, whose balance of depth and width is optimized for high-resolution medical images. 3) Pretraining the network on screening BI-RADS classification, a related task with more noisy labels. 4) Combining multiple input views in an optimal way among a number of possible choices. To validate our model, we conducted a reader study with 14 readers, each reading 720 screening mammogram exams, and show that our model is as accurate as experienced radiologists when presented with the same data. We also show that a hybrid model, averaging the probability of malignancy predicted by a radiologist with a prediction of our neural network, is more accurate than either of the two separately. To further understand our results, we conduct a thorough analysis of our network's performance on different subpopulations of the screening population, the model's design, training procedure, errors, and properties of its internal representations. Our best models are publicly available at https://github.com/nyukat/breast_cancer_classifier.

Sentinel lymph node positivity in patients undergoing mastectomies for ductal carcinoma in situ (DCIS)

Current guidelines recommend sentinel lymph node biopsy (SLNB) for patients undergoing mastectomy for a preoperative diagnosis of ductal carcinoma in situ (DCIS). We examined the factors associated with sentinel lymph node positivity for patients undergoing mastectomy for a diagnosis of DCIS on preoperative core biopsy (PCB). The Institutional Breast Cancer Database was queried for patients with PCB demonstrating pure DCIS followed by mastectomy and SLNB from 2010 to 2018. Patients were divided according to final pathology (DCIS or invasive cancer). Clinico-pathologic variables were analyzed using Pearson's chi-squared, Wilcoxon Rank-Sum and logistic regression. Of 3145 patients, 168(5%) had pure DCIS on PCB and underwent mastectomy with SLNB. On final mastectomy pathology, 120(71%) patients had DCIS with 0 positive sentinel lymph nodes (PSLNs) and 48(29%) patients had invasive carcinoma with 5(10%) cases of ≥1 PSLNs. Factors positively associated with upstaging to invasive cancer in univariate analysis included age (P = .0289), palpability (P < .0001), extent of disease on imaging (P = .0121), mass on preoperative imaging (P = .0003), multifocality (P = .0231) and multicentricity (P = .0395). In multivariate analysis, palpability (P = .0080), extent of disease on imaging (P = .0074) and mass on preoperative imaging (P = .0245) remained significant (Table 2). In a subset of patients undergoing mastectomy for DCIS with limited disease on preoperative evaluation, SLNB may be omitted as the risk of upstaging is low. However, patients who present with clinical findings of palpability, large extent of disease on imaging and mass on preoperative imaging have a meaningful risk of upstaging to invasive cancer, and SLNB remains important for management.

The relationship of breast density in mammography and magnetic resonance imaging in women with triple negative breast cancer

PURPOSE

To evaluate the relationship between mammographic density, background parenchymal enhancement and fibroglandular tissue on MRI in women with triple negative breast cancer (TNBC) compared to women with non-triple negative breast cancer (non-TNBC).

METHODS

The institutional Breast Cancer Database was queried to identify the clinicopathologic and imaging characteristics among women who underwent mammography and breast MRI between 2010-2018. Statistical analyses included Pearson's Chi Square, Wilcoxon Rank-Sum and logistic regression.

RESULTS

Of 2995 women, 225 (7.5 %) had TNBC with a median age of 60 years (23-96) and median follow-up of 5.69 years. Compared to women with non-TNBC, TNBC was associated with African-American race 36/225 (16 %), BRCA1,2 positivity 34/225 (15.1 %), previous history of breast cancer 35/225 (15.6 %), presenting on breast exam 126/225 (56 %) or MRI 13/225 (5.8 %), palpability 133/225 (59.1 %), more invasive ductal carcinoma (IDC) 208/225 (92.4 %), higher stage (stage III) 37/225 (16.5 %), higher grade (grade 3) 186/225 (82.7 %) (all p < 0.001), lower mammographic breast density (MBD) 18/225 (8 %) (p = 0.04), lower fibroglandular tissue (FGT) 17/225 (7.6 %) (p = 0.01), and lower background parenchymal enhancement (BPE) 89/225 (39.8 %) (p = 0.02). Nine of 225 (4 %) women with TNBC experienced recurrence with no significant association with MBD, FGT, or BPE. There was no significant difference in median age of our TNBC and non-TNBC cohorts.

CONCLUSIONS

The higher proportion of women with lower MBD, FGT and BPE in women with TNBC suggests that MBD, amount of FGT and degree of BPE may be associated with breast cancer risk in women with TNBC.

Preliminary study: Breast cancers can be well seen on 3T breast MRI with a half-dose of gadobutrol

BACKGROUND

Dynamic contrast enhanced (DCE) breast MRI is highly sensitive for breast cancer and requires gadolinium-based contrast agents (GBCA)s, which have potential safety concerns.

PURPOSE

Test whether breast cancers imaged by 3T DCE breast MRI with 0.05 mmol/kg of gadobutrol are detectable.

METHODS

Analysis of 3T DCE breast MRIs with half dose of gadobutrol from patients included in an IRB-approved and HIPPA-compliant prospective study of breast PET/MRI. Between 11/7/2014 and 3/2/2018, 41 consecutive women with biopsy-proven breast cancer that was at least 2 cm, multi-focal or multi-centric, had axillary metastasis, or had skin involvement who gave informed consent were included. Two breast radiologists independently recorded lesion conspicuity on a 4-point scale (0 = not seen, 1 = questionably seen, 2 = adequately seen, 3 = certainly seen), and measured the lesion. Size was compared between radiologists and with size on available mammogram, ultrasound, MRI, and surgical pathology. Inter-reader agreement was assessed by kappa coefficient for conspicuity. Lesion size comparisons were assessed using the Spearman rank correlation.

RESULTS

In 40 patients (ages 28.4-80.5, 51.9 years), there were 49 cancers. 10.1% of lesions were 1 cm or less and 26.5% of lesions were 2 cm or less. Each reader detected 49/49 cancers. Conspicuity scores ranged from 2 to 3, mean 2.9/3 for both readers (p = 0.47). Size on half-dose 3T DCE-MRI correlated with size on surgical pathology (r = 0.6, p = 0.03) while size on mammogram and ultrasound did not (r = 0.25, p = 0.46; r = 0.25, p = 0.42).

CONCLUSION

All breast cancers in this cohort, as small as 0.4 cm, were seen on 3T DCE breast MRI with 0.05 mmol/kg dose of gadobutrol.

Breast MRI screening for average-risk women: A monte carlo simulation cost-benefit analysis

BACKGROUND

Screening high-risk women for breast cancer with MRI is cost-effective, with increasing cost-effectiveness paralleling increasing risk. However, for average-risk women cost is considered a major limitation to mass screening with MRI.

PURPOSE

To perform a cost-benefit analysis of a simulated breast cancer screening program for average-risk women comparing MRI with mammography.

STUDY TYPE

Population simulation study.

POPULATION/SUBJECTS

Five million (M) hypothetical women undergoing breast cancer screening.

FIELD STRENGTH/SEQUENCE

Simulation based primarily on Kuhl et al⁸ study utilizing 1.5T MRI with an axial bilateral 2D multisection gradient-echo dynamic series (repetition time / echo time 250/4.6 msec; flip angle, 90°) with a full 512 × 512 acquisition matrix and a sensitivity encoding factor of two, performed prior to and four times after bolus injection of 0.1 mmol of gadobutrol per kg of body weight (Gadovist; Bayer, Germany). An axial T₂ -weighted fast spin-echo sequence with identical anatomic parameters was also included.

ASSESSMENT

A Monte Carlo simulation utilizing Medicare reimbursement rates to calculate input variable costs was developed to compare 5M women undergoing breast cancer screening with either triennial MRI or annual mammography, 2.5M in each group, over 30 years.

STATISTICAL TESTS

Expected recall rates, BI-RADS 3, BI-RADS 4/5 cases and cancer detection rates were determined from published literature with calculated aggregate costs including resultant diagnostic/follow-up imaging and biopsies.

RESULTS

Baseline screening of 2.5M women with breast MRI cost $1.6 billion (B), 3× higher than baseline mammography screening ($0.54B). With subsequent screening, MRI screening is more cost-effective than mammography screening in 24 years ($13.02B vs. $13.03B). MRI screening program costs are largely driven by cost per MRI exam ($549.71). A second simulation model was performed based on MRI Medicare reimbursement trends using a lower MRI cost ($400). This yielded a cost-effective benefit compared to mammography screening in less than 6 years ($3.41B vs. $3.65B), with over a 22% cost reduction relative to mammography screening in 12 years and reaching a 38% reduction in 30 years.

DATA CONCLUSION

Despite higher initial cost of a breast MRI screening program for average-risk women, there is ultimately a cost savings over time compared with mammography. This estimate is conservative given cost-benefit of additional/earlier breast cancers detected by breast MRI were not accounted for.

LEVEL OF EVIDENCE

3 Technical Efficacy Stage: 6 J. Magn. Reson. Imaging 2019.

Preliminary analysis: Background parenchymal 18F-FDG uptake in breast cancer patients appears to correlate with background parenchymal enhancement and to vary by distance from the index cancer

PURPOSE

To investigate how breast parenchymal uptake (BPU) of 18F-FDG on positron emission tomography/ magnetic resonance imaging (PET/MRI) in patients with breast cancer is related to background parenchymal enhancement (BPE), amount of fibroglandular tissue (FGT), and age, as well as whether BPU varies as a function of distance from the primary breast cancer.

MATERIALS AND METHODS

In this institutional review board (IRB)-approved retrospective study, 40 patients (all female, ages 32-80 years, mean 52 years) gave informed consent prior to undergoing contrast enhanced breast PET/MRI from 3/2015 to 2/2018. Of the 40 patients, 6 were excluded for multicentric or bilateral cancers, 1 for current lactation and 6 because the raw data from their scans were corrupted. The remaining 27 patients (all female, ages 33 to 80 years, mean age 53 years) comprised the study population. Prone PET and contrast-enhanced MR data were acquired simultaneously on a 3-T integrated PET/ MR system. BPU was measured as SUVmax of a 1.5 cm³ volume of interest 1) in the same quadrant of the ipsilateral breast, 5 mm from the index lesion; 2) in the opposite quadrant of the ipsilateral breast; and 3) in contralateral breast, quadrant matched to the opposite quadrant of the ipsilateral breast. The maximum standardized uptake value (SUVmax) of the index cancer was measured using a VOI that included the entire volume of the index lesion. Bleed from the primary tumor was corrected for (PET edge, MIM). FGT and BPE was assessed by 2 readers on a 4-point scale in accordance with BI-RADS lexicon. The Wilcoxon signed rank test and the Spearman rank correlation test were performed.

RESULTS

BPU was significantly greater in the same quadrant as the breast cancer as compared with the opposite quadrant of the same breast (p < 0.001 for both readers) and was significantly greater in the opposite quadrant of the same breast compared to the matched quadrant of the contralateral breast (p = 0.002 for reader 1 and <0.001 for reader 2). While the FGT SUVmax in the same quadrant as the cancer correlated significantly with SUVmax of the index lesion, the FGT SUVmax in the opposite quadrant of the same breast and in the matched quadrant of the contralateral breast did not. The FGT SUVmax in the contralateral breast positively correlated with the degree of BPE and negatively correlated with age, but did not show a significant correlation with the amount of FGT for either reader.

CONCLUSION

There appears to be an inverse correlation between metabolic activity of normal breast parenchyma and distance from the index cancer. BPU significantly correlates with BPE.

Evaluation of association between degree of background parenchymal enhancement on MRI and breast cancer subtype

PURPOSE

Evaluate possible association between BPE and breast cancer tumor type/prognostic markers.

METHODS

IRB approved retrospective study from 1/2010-1/2014 identified 328 patients who had breast MRI and available clinical/pathology data. BPE was categorized according to BI-RADS. The association between BPE and breast cancer molecular subtype/prognostic factors was evaluated.

RESULTS

No significant association was present between high BPE and the following: HER2+ tumors, basal tumors, tumors with axillary nodal disease, high nuclear grade tumors, high Ki-67 index tumors or larger tumors.

CONCLUSION

Patients with high BPE may be at increased risk for breast cancer but not necessarily for those cancer subtypes with a poor prognosis.

Director gliding in a nematic liquid crystal layer: Quantitative comparison with experiments

The interaction between nematic liquid crystals and polymer-coated substrates may lead to slow reorientation of the easy axis (so-called "director gliding") when a prolonged external field is applied. We consider the experimental evidence of zenithal gliding observed by Joly et al. [Phys. Rev. E 70, 050701 (2004)PLEEE81539-375510.1103/PhysRevE.70.050701] and Buluy et al. [J. Soc. Inf. Disp. 14, 603 (2006)1071-092210.1889/1.2235686] as well as azimuthal gliding observed by S. Faetti and P. Marianelli [Liq. Cryst. 33, 327 (2006)LICRE60267-829210.1080/02678290500512227], and we present a simple, physically motivated model that captures the slow dynamics of gliding, both in the presence of an electric field and after the electric field is turned off. We make a quantitative comparison of our model results and the experimental data and conclude that our model explains the gliding evolution very well.

Does breast MRI background parenchymal enhancement indicate metabolic activity? Qualitative and 3D quantitative computer imaging analysis

PURPOSE

To investigate whether the degree of breast magnetic resonance imaging (MRI) background parenchymal enhancement (BPE) is associated with the amount of breast metabolic activity measured by breast parenchymal uptake (BPU) of 18F-FDG on positron emission tomography / computed tomography (PET/CT).

MATERIALS AND METHODS

An Institutional Review Board (IRB)-approved retrospective study was performed. Of 327 patients who underwent preoperative breast MRI from 1/1/12 to 12/31/15, 73 patients had 18F-FDG PET/CT evaluation performed within 1 week of breast MRI and no suspicious findings in the contralateral breast. MRI was performed on a 1.5T or 3.0T system. The imaging sequence included a triplane localizing sequence followed by sagittal fat-suppressed T₂ -weighted sequence, and a bilateral sagittal T₁ -weighted fat-suppressed fast spoiled gradient-echo sequence, which was performed before and three times after a rapid bolus injection (gadobenate dimeglumine, Multihance; Bracco Imaging; 0.1 mmol/kg) delivered through an IV catheter. The unaffected contralateral breast in these 73 patients underwent BPE and BPU assessments. For PET/CT BPU calculation, a 3D region of interest (ROI) was drawn around the glandular breast tissue and the maximum standardized uptake value (SUV_max ) was determined. Qualitative MRI BPE assessments were performed on a 4-point scale, in accordance with BI-RADS categories. Additional 3D quantitative MRI BPE analysis was performed using a previously published in-house technique. Spearman's correlation test and linear regression analysis was performed (SPSS, v. 24).

RESULT

The median time interval between breast MRI and 18F-FDG PET/CT evaluation was 3 days (range, 0-6 days). BPU SUV_max mean value was 1.6 (SD, 0.53). Minimum and maximum BPU SUV_max values were 0.71 and 4.0. The BPU SUV_max values significantly correlated with both the qualitative and quantitative measurements of BPE, respectively (r(71) = 0.59, P < 0.001 and r(71) = 0.54, P < 0.001). Qualitatively assessed high BPE group (BI-RADS 3/4) had significantly higher BPU SUV_max of 1.9 (SD = 0.44) compared to low BPE group (BI-RADS 1/2) with an average BPU SUV_max of 1.17 (SD = 0.32) (P < 0.001). On linear regression analysis, BPU SUV_max significantly predicted qualitative and quantitative measurements of BPE (β = 1.29, t(71) = 3.88, P < 0.001 and β = 19.52, t(71) = 3.88, P < 0.001).

CONCLUSION

There is a significant association between breast BPU and BPE, measured both qualitatively and quantitatively. Increased breast cancer risk in patients with high MRI BPE could be due to elevated basal metabolic activity of the normal breast tissue, which may provide a susceptible environment for tumor growth.

LEVEL OF EVIDENCE

3 Technical Efficacy: Stage 3 J. Magn. Reson. Imaging 2018;47:753-759.

Unravelling tumour heterogeneity using next-generation imaging: radiomics, radiogenomics, and habitat imaging

Tumour heterogeneity in cancers has been observed at the histological and genetic levels, and increased levels of intra-tumour genetic heterogeneity have been reported to be associated with adverse clinical outcomes. This review provides an overview of radiomics, radiogenomics, and habitat imaging, and examines the use of these newly emergent fields in assessing tumour heterogeneity and its implications. It reviews the potential value of radiomics and radiogenomics in assisting in the diagnosis of cancer disease and determining cancer aggressiveness. This review discusses how radiogenomic analysis can be further used to guide treatment therapy for individual tumours by predicting drug response and potential therapy resistance and examines its role in developing radiomics as biomarkers of oncological outcomes. Lastly, it provides an overview of the obstacles in these emergent fields today including reproducibility, need for validation, imaging analysis standardisation, data sharing and clinical translatability and offers potential solutions to these challenges towards the realisation of precision oncology.

Effects of flexoelectricity and weak anchoring on a Freedericksz transition cell

We consider a mathematical model that consists of a nematic liquid crystal layer sandwiched between two parallel bounding plates, across which an external field is applied. We investigate how the number and type of solutions for the director orientation within the layer change as the field strength, anchoring conditions, and material properties of the nematic liquid crystal layer vary. In particular, we focus on how the inclusion of flexoelectric effects alters the Freedericksz and saturation thresholds.

Cystic metastatic lymph nodes in malignant melanoma: a case report

Melanoma is a rare type of skin cancer with a high mortality rate. Local invasion and metastatic spread are primarily responsible for the morbidity and mortality of melanoma. While metastatic lesions vary from cystic to solid, cystic metastases can be challenging to diagnose. Up to date, there are only a few published studies that describe cystic metastases in melanoma and other conditions such as lymphoma, squamous cell carcinoma and thyroid papillary carcinoma. We describe a case of cystic metastatic axillary lymph nodes in a patient with subungual acral lentiginous melanoma and the challenges to reaching an accurate diagnosis.

Quantitative 3D breast magnetic resonance imaging fibroglandular tissue analysis and correlation with qualitative assessments: a feasibility study

BACKGROUND

The amount of fibroglandular tissue (FGT) has been linked to breast cancer risk based on mammographic density studies. Currently, the qualitative assessment of FGT on mammogram (MG) and magnetic resonance imaging (MRI) is prone to intra and inter-observer variability. The purpose of this study is to develop an objective quantitative FGT measurement tool for breast MRI that could provide significant clinical value.

METHODS

An IRB approved study was performed. Sixty breast MRI cases with qualitative assessment of mammographic breast density and MRI FGT were randomly selected for quantitative analysis from routine breast MRIs performed at our institution from 1/2013 to 12/2014. Blinded to the qualitative data, whole breast and FGT contours were delineated on T1-weighted pre contrast sagittal images using an in-house, proprietary segmentation algorithm which combines the region-based active contours and a level set approach. FGT (%) was calculated by: [segmented volume of FGT (mm(3))/(segmented volume of whole breast (mm(3))] ×100. Statistical correlation analysis was performed between quantified FGT (%) on MRI and qualitative assessments of mammographic breast density and MRI FGT.

RESULTS

There was a significant positive correlation between quantitative MRI FGT assessment and qualitative MRI FGT (r=0.809, n=60, P<0.001) and mammographic density assessment (r=0.805, n=60, P<0.001). There was a significant correlation between qualitative MRI FGT assessment and mammographic density assessment (r=0.725, n=60, P<0.001). The four qualitative assessment categories of FGT correlated with the calculated mean quantitative FGT (%) of 4.61% (95% CI, 0-12.3%), 8.74% (7.3-10.2%), 18.1% (15.1-21.1%), 37.4% (29.5-45.3%).

CONCLUSIONS

Quantitative measures of FGT (%) were computed with data derived from breast MRI and correlated significantly with conventional qualitative assessments. This quantitative technique may prove to be a valuable tool in clinical use by providing computer generated standardized measurements with limited intra or inter-observer variability.

Three-Dimensional Quantitative Validation of Breast Magnetic Resonance Imaging Background Parenchymal Enhancement Assessments

The magnetic resonance imaging (MRI) background parenchymal enhancement (BPE) and its clinical significance as a biomarker of breast cancer risk has been proposed based on qualitative studies. Previous BPE quantification studies lack appropriate correlation with BPE qualitative assessments. The purpose of this study is to validate our three-dimensional BPE quantification method with standardized BPE qualitative cases. An Institutional Review Board-approved study reviewed 500 consecutive magnetic resonance imaging cases (from January 2013-December 2014) using a strict inclusion criteria and 120 cases that best represented each of the BPE qualitative categories (minimal or mild or moderate or marked) were selected. Blinded to the qualitative data, fibroglandular tissue contours of precontrast and postcontrast images were delineated using an in-house, proprietary segmentation algorithm. Metrics of BPE were calculated including %BPE ([ratio of BPE volume to fibroglandular tissue volume] × 100) at multiple threshold levels to determine the optimal cutoff point for BPE quantification that best correlated with the reference BPE qualitative cases. The highest positive correlation was present at ×1.5 precontrast average signal intensity threshold level (r = 0.84, P < 0.001). At this level, the BPE qualitative assessment of minimal, mild, moderate, and marked correlated with the mean quantitative %BPE of 14.1% (95% CI: 10.9-17.2), 26.1% (95% CI: 22.8-29.3), 45.9% (95% CI: 40.2-51.7), and 74.0% (95% CI: 68.6-79.5), respectively. A one-way analysis of variance with post-hoc analysis showed that at ×1.5 precontrast average signal intensity level, the quantitative %BPE measurements best differentiated the four reference BPE qualitative groups (F [3,117] = 106.8, P < 0.001). Our three-dimensional BPE quantification methodology was validated using the reference BPE qualitative cases and could become an invaluable clinical tool to more accurately assess breast cancer risk and to test chemoprevention strategies.

Substrate-induced gliding in a nematic liquid crystal layer

We consider the interaction between nematic liquid crystals (NLCs) and polymer substrates. Such substrates can interact with NLCs, exhibiting a phenomenon known as director gliding: the preferred orientation of the NLC molecules at the interface changes on time scales that are slow relative to the elastic relaxation time scale of the NLC. We present two models for gliding, inspired by experiments that investigate the interaction between the NLC and a polymer substrate. These models, though simple, lead to nontrivial results, including loss of bistability under gliding. Perhaps surprisingly, we find that externally imposed switching between the steady states of a bistable system may reverse the effect of gliding, preventing loss of bistability if switching is sufficiently frequent. Our findings may be of relevance to a variety of technological applications involving liquid crystal devices, and particularly to a new generation of flexible liquid crystal displays that implement polymeric substrates.

Electric-field variations within a nematic-liquid-crystal layer

A thin layer of nematic liquid crystal (NLC) across which an electric field is applied is a setup of great industrial importance in liquid crystal display devices. There is thus a large literature modeling this situation and related scenarios. A commonly used assumption is that an electric field generated by electrodes at the two bounding surfaces of the layer will produce a field that is uniform: that is, the presence of NLC does not affect the electric field. In this paper, we use calculus of variations to derive the equations coupling the electric potential to the orientation of the NLC's director field, and use a simple one-dimensional model to investigate the limitations of the uniform field assumption in the case of a steady applied field. The extension of the model to the unsteady case is also briefly discussed.

Absence of the glucagon-like peptide-1 receptor does not affect the metabolic phenotype of mice with liver-specific G(s)α deficiency

The stimulatory G protein α-subunit (G(s)α) couples hormone and other receptors to the generation of intracellular cAMP. We previously showed that mice with liver-specific G(s)α deficiency [liver-specific G(s)α knockout (LGsKO) mice] had reduced adiposity and improved glucose tolerance associated with increased glucose-stimulated insulin secretion, pancreatic islet hyperplasia, and very high serum glucagon and glucagon-like peptide 1 (GLP-1) levels. Because GLP-1 is known to stimulate insulin secretion and to have effects on energy balance, we mated LGsKO mice with germline GLP-1 receptor (GLP-1R) knockout mice (Glp1r(-/-)) and compared LGsKO to double-knockout (LGs/Glp1r(-/-)) mice to determine the contribution of excess GLP-1R signaling to the LGsKO phenotype. Loss of the GLP-1R failed to reverse most of the metabolic features of LGsKO mice, including reduced fat mass, increased glucose tolerance, and second-phase glucose-stimulated insulin secretion, islet cell hyperplasia, and very high glucagon and GLP-1 levels. However, loss of GLP-1R impaired first-phase insulin secretion in mice with or without liver-specific G(s)α deficiency. Thus, excess GLP-1 action (or at least through GLP-1R) does not contribute to the LGsKO metabolic phenotype, and other unknown factors involved in the cross talk between the liver G(s)α/cAMP pathway and pancreatic islet function need to be further elucidated.