Deep learning model to predict Ki-67 expression of breast cancer using digital breast tomosynthesis

BACKGROUND

Developing a deep learning (DL) model for digital breast tomosynthesis (DBT) images to predict Ki-67 expression.

METHODS

The institutional review board approved this retrospective study and waived the requirement for informed consent from the patients. Initially, 499 patients (mean age: 50.5 years, range: 29-90 years) referred to our hospital for breast cancer were participated, 126 patients with pathologically confirmed breast cancer were selected and their Ki-67 expression measured. The Xception architecture was used in the DL model to predict Ki-67 expression levels. The high Ki-67 vs low Ki-67 expression diagnostic performance of our DL model was assessed by accuracy, sensitivity, specificity, areas under the receiver operating characteristic curve (AUC), and by using sub-datasets divided by the radiological characteristics of breast cancer.

RESULTS

The average accuracy, sensitivity, specificity, and AUC were 0.912, 0.629, 0.985, and 0.883, respectively. The AUC of the four subgroups separated by radiological findings for the mass, calcification, distortion, and focal asymmetric density sub-datasets were 0.890, 0.750, 0.870, and 0.660, respectively.

CONCLUSIONS

Our results suggest the potential application of our DL model to predict the expression of Ki-67 using DBT, which may be useful for preoperatively determining the treatment strategy for breast cancer.

Deep learning model for predicting the presence of stromal invasion of breast cancer on digital breast tomosynthesis

To develop a deep learning (DL)-based algorithm to predict the presence of stromal invasion in breast cancer using digital breast tomosynthesis (DBT). Our institutional review board approved this retrospective study and waived the requirement for informed consent from the patients. Initially, 499 patients (mean age 50.5 years, age range, 29-90 years) who were referred to our hospital under the suspicion of breast cancer and who underwent DBT between March 1 and August 31, 2019, were enrolled in this study. Among the 499 patients, 140 who underwent surgery after being diagnosed with breast cancer were selected for the analysis. Based on the pathological reports, the 140 patients were classified into two groups: those with non-invasive cancer (n = 20) and those with invasive cancer (n = 120). VGG16, Resnet50, DenseNet121, and Xception architectures were used as DL models to differentiate non-invasive from invasive cancer. The diagnostic performance of the DL models was assessed based on the area under the receiver operating characteristic curve (AUC). The AUC for the four models were 0.56 [95% confidence intervals (95% CI) 0.49-0.62], 0.67 (95% CI 0.62-0.74), 0.71 (95% CI 0.65-0.75), and 0.75 (95% CI 0.69-0.81), respectively. Our proposed DL model trained on DBT images is useful for predicting the presence of stromal invasion in breast cancer.

Deep Learning for Differentiation of Breast Masses Detected by Screening Ultrasound Elastography

Recently, deep learning using convolutional neural networks (CNNs) has yielded consistent results in image-pattern recognition. This study was aimed at investigating the effectiveness of deep learning using CNNs to differentiate benign and malignant breast masses identified by elastography on ultrasound screening. A data set of the elastography images of 245 breast masses (146 benign, 99 malignant) in 239 consecutive patients was retrospectively obtained. The data set was randomly split into training (55%), validation (25%) and test (20%) cohorts. A deep learning model predicting the probability of malignancy was constructed using GoogLeNet architectures (pre-trained by ImageNet) with 50 epochs. The model was then applied to the test data, and the results were compared with those obtained by evaluating the fat-to-lesion ratio (FLR) and by a 5-point visual color assessment (elasticity score). The receiver operating characteristic (ROC) curve was calculated to evaluate the performance of the model. The DeLong test was used to compare the areas under the ROC curve (AUCs). The CNN, FLR and elasticity score had a sensitivity of 0.800, 0.800 and 0.350; specificity of 0.966, 0.586 and 0.931; accuracy of 0.898, 0.673 and 0.694; positive predictive value of 0.941, 0.571 and 0.778; negative predictive value of 0.875, 0.810 and 0.675; and AUC of 0.895, 0.693 and 0.641, respectively. The AUC of the CNN was significantly higher than that of the FLR or elasticity score (p < 0.001). A CNN-based deep learning model for predicting benign or malignant breast masses revealed better diagnostic performance than did FLR or elasticity score-based estimations on ultrasound elastography. The CNN-based model also increased the positive predictive value from 57%-78% to 94%. Therefore, this model may reduce unnecessary biopsy recommendations for masses detected on breast ultrasound screening.

Clinicopathological and ultrasound characteristics of breast cancer in BRCA1 and BRCA2 mutation carriers

PURPOSE

BRCA1 and BRCA2 tumors exhibit different characteristics. This study aimed to assess and compare the ultrasound findings and pathologic features of BRCA1 and BRCA2 breast cancers. To our knowledge, this is the first study to examine the mass formation, vascularity, and elasticity in breast cancers of BRCA-positive Japanese women.

METHODS

We identified patients with breast cancer harboring BRCA1 or BRCA2 mutations. After excluding patients who underwent chemotherapy or surgery before the ultrasound, we evaluated 89 cancers in BRCA1-positive and 83 in BRCA2-positive patients. The ultrasound images were reviewed by three radiologists in consensus. Imaging features, including vascularity and elasticity, were assessed. Pathological data, including tumor subtypes, were reviewed.

RESULTS

Significant differences in tumor morphology, peripheral features, posterior echoes, echogenic foci, and vascularity were observed between BRCA1 and BRCA2 tumors. BRCA1 breast cancers tended to be posteriorly accentuating and hypervascular. In contrast, BRCA2 tumors were less likely to form masses. In cases where a tumor formed a mass, it tended to show posterior attenuation, indistinct margins, and echogenic foci. In pathological comparisons, BRCA1 cancers tended to be triple-negative subtypes. In contrast, BRCA2 cancers tended to be luminal or luminal-human epidermal growth factor receptor 2 subtypes.

CONCLUSION

In the surveillance of BRCA mutation carriers, radiologists should be aware that the morphological differences between tumors are quite different between BRCA1 and BRCA2 patients.

Deep learning model for breast cancer diagnosis based on bilateral asymmetrical detection (BilAD) in digital breast tomosynthesis images

The purpose of this study was to develop a deep learning model to diagnose breast cancer by embedding a diagnostic algorithm that examines the asymmetry of bilateral breast tissue. This retrospective study was approved by the institutional review board. A total of 115 patients who underwent breast surgery and had pathologically confirmed breast cancer were enrolled in this study. Two image pairs [230 pairs of bilateral breast digital breast tomosynthesis (DBT) images with 115 malignant tumors and contralateral tissue (M/N), and 115 bilateral normal areas (N/N)] were generated from each patient enrolled in this study. The proposed deep learning model is called bilateral asymmetrical detection (BilAD), which is a modified convolutional neural network (CNN) model of Xception with two-dimensional tensors for bilateral breast images. BilAD was trained to classify the differences between pairs of M/N and N/N datasets. The results of the BilAD model were compared to those of the unilateral control CNN model (uCNN). The results of BilAD and the uCNN were as follows: accuracy, 0.84 and 0.75; sensitivity, 0.73 and 0.58; and specificity, 0.93 and 0.92, respectively. The mean area under the receiver operating characteristic curve of BilAD was significantly higher than that of the uCNN (p = 0.02): 0.90 and 0.84, respectively. The proposed deep learning model trained by embedding a diagnostic algorithm to examine the asymmetry of bilateral breast tissue improves the diagnostic accuracy for breast cancer.

The location of unilateral axillary lymphadenopathy after COVID-19 vaccination compared with that of metastasis from breast cancer without vaccination

PURPOSE

Unilateral axillary lymphadenopathy is known to occur after coronavirus disease (COVID-19) vaccination. Post-vaccination lymphadenopathy may mimic the metastatic lymph nodes in breast cancer, and it is challenging to distinguish between them. This study investigated whether the localization of axillary lymphadenopathy on magnetic resonance imaging (MRI) could be used to distinguish reactive lymphadenopathy after COVID-19 vaccines from metastatic nodes.

MATERIALS AND METHODS

We retrospectively examined preoperative MRI images of 684 axillae in 342 patients who underwent breast cancer surgery from June to October 2021. Lymphadenopathy was defined as cortical thickening or short axis ≥ 5 mm. The axilla was divided into ventral and dorsal parts on the axial plane using a perpendicular line extending from the most anterior margin of the muscle group, including the deltoid, latissimus dorsi, or teres major muscles, relative to a line along the lateral chest wall. We recorded the presence or absence of axillary lymphadenopathy in each area and the number of visible lymph nodes.

RESULTS

Of 80 axillae, 41 and 39 were included in the vaccine and metastasis groups, respectively. The median time from the last vaccination to MRI was 19 days in the vaccine group. The number of visible axillary lymph nodes was significantly higher in the vaccine group (median, 15 nodes) than in the metastasis group (7 nodes) (P < 0.001). Dorsal lymphadenopathy was observed in 16 (39.0%) and two (5.1%) axillae in the vaccine and metastasis groups, respectively (P < 0.001). If the presence of both ventral and dorsal lymphadenopathy is considered indicative of vaccine-induced reaction, this finding has a sensitivity of 34.1%, specificity of 97.4%, and positive and negative predictive values of 93.3％ and 58.5%, respectively.

CONCLUSION

The presence of deep axillary lymphadenopathy may be an important factor for distinguishing post-vaccination lymphadenopathy from metastasis. The number of axillary lymph nodes may also help.

Why is the depth/width ratio of a typical fibroadenoma small in breast ultrasonography?

PURPOSE

Typical myxomatous fibroadenomas have a small depth/width (D/W) ratio on ultrasonography. The small D/W ratio of fibroadenomas is speculated to be caused by the softness of the mass and its orientation along the longitudinal aspect of the ductal elements without adhesion to the surrounding tissue; however, this has not been clearly proven. This study aimed to confirm the reason why fibroadenomas present with a small D/W ratio on ultrasonography.

METHODS

We retrospectively analyzed imaging data from 17 patients who were diagnosed with typical fibroadenomas on ultrasonography and who underwent magnetic resonance imaging (MRI) at our hospital.

RESULTS

The median D/W ratio obtained from ultrasonography images was 0.48 (0.32-0.67), while that obtained from MRI was 1.38 (0.62-1.68). The D/W ratios calculated from MRI were significantly greater than those calculated from ultrasonography images (p < 0.001). The D/W ratio obtained using ultrasonography was not greater than the D/W ratio obtained using MRI in any of the cases.

CONCLUSION

This study revealed that the small D/W ratio of fibroadenomas on ultrasonography may be attributable to the horizontal force acting on the breast against the chest wall in the supine position, the elasticity of the fibroadenoma, and the lack of adhesion between the mass and surrounding tissue.

The relationship between postoperative ligament balance and preoperative varus deformity in total knee arthroplasty

We hypothesize that in knees with severe varus deformities, varus-valgus ligament imbalance tends to remain postoperatively after total knee arthroplasty. The purpose of this study was to evaluate the correlation between preoperative varus deformity and postoperative ligament balance quantitatively measured by stress radiograph using Telos SE in total knee arthroplasty. In this study, 44 knee arthroplasties in 32 patients were evaluated. We defined the angle in varus and valgus stress as "varus angle" and "valgus angle," and the sum of varus angle and valgus angle as "sum of varus-valgus angle." There was a significant correlation between preoperative lateral femoral angle and varus angle (p < 0.0001, r = 0.56), which means that postoperative ligament imbalance tends to remain in knees with preoperative varus deformities. There was a significant correlation between the postoperative period and the sum of varus-valgus angle, which suggests that knees with total knee arthroplasty have potential to increase laxity postoperatively.

Intra-articular detachment of the Endobutton more than 18 months after anterior cruciate ligament reconstruction

We report a case of detachment of an Endobutton (Acufex Microsurgical, Mansfield MA) used for femoral fixation of a reconstructed anterior cruciate ligament. The Endobutton, which was confirmed to be in place on the suprapatellar space of the femur by radiograph 18 months postoperatively, was found in the popliteal space by radiograph 25 months after surgery. This is a rare complication, but our case suggests that the Endobutton should not be fixed too distal close to the femoral groove.

Two-bundle reconstruction of the anterior cruciate ligament using semitendinosus tendon with endobuttons: operative technique and preliminary results

We carried out two-bundle reconstruction of the anterior cruciate ligament (ACL) using multi-strand semitendinosus tendon for the purpose of getting better stability under aggressive rehabilitation by putting the graft in the normal anatomy with minimized notch-plasty. The drill guide position was determined using two-directional radiography in hyperextension. The two-bundle procedure was performed using the inside-out technique for grafting and two Endobuttons (Acufex Microsurgical, Mansfield, MA) for femoral graft fixation. The clinical outcomes 2 years postoperatively of 54 of 62 consecutive patients were reported. The preliminary results suggested that the two-bundle procedure showed a better trend with respect to anterior stability compared with those of our previous experience using the single-bundle technique under the same aggressive rehabilitation. The two-bundle procedures have several theoretical advantages over single-bundle with multi-strand tendon graft. The present two-bundle reconstruction is recommended to result in better anterior stability with minimized notch-plasty and with no serious complications.

Effects of aggressive early rehabilitation on the outcome of anterior cruciate ligament reconstruction with multi-strand semitendinosus tendon

To evaluate the effects of aggressive early rehabilitation on the clinical outcome of anterior cruciate ligament reconstruction using semitendinosus (and gracilis) tendon, 103 of 110 consecutive patients who underwent ACL reconstruction using multistrand semitendinosus tendon (ST) or the central one-third of patellar tendon with bony attachments (BTB) were analyzed prospectively. Subjectively, the Lysholm score was not different among the groups. The Lachman test indicated a trend of less negative grade in the ST men's group than that in the BTB men's group. On the patellofemoral grinding test, only women patients of both groups showed pain, with less positive crepitation in the ST group than in the BTB group. KT measurements at manual maximum showed more patients with more than 5 mm differences in the ST group than in the BTB group. The results of this study suggest that aggressive early rehabilitation after the ACL reconstruction using the semitendinosus (and gracilis) tendon has more risk of residual laxity than with the BTB.

Objective factors affecting overall subjective evaluation of recovery after anterior cruciate ligament reconstruction

The goal of this prospective study was to determine how objective measurements affect the overall subjective evaluation of recovery after anterior cruciate ligament (ACL) reconstruction and to evaluate the effects of graft material, residual instability and sporting activity on patient satisfaction. Ninety-seven patients with unilateral ACL injuries whose ACL was reconstructed using either a multi-strand semitendinosus (ST) graft or a central-third bone-patellar tendon-bone (BTB) graft were followed for an average of 30 months. An "overall subjective recovery score" was derived from the patients' evaluation of function of the operated knee as a percentage of the unoperated knee. The mean overall subjective recovery score at follow-up was 80% (range, 20% to 100%). This study strongly suggested that integrity of the knee extension mechanism, that is, good recovery of knee extension strength with achievement of full extension and no problems in the patellofemoral joint, is the most important factor in patient satisfaction after ACL reconstruction.

Subtalar instability following lateral ligament injuries of the ankle

A stress radiograph of the subtalar joint was taken using Telos equipment, while the X-ray beam was directed onto the posterior subtalar joint at angles of 30 degrees latero-medially and 40 degrees caudocranially. From this radiograph the subtalar tilt angle was measured as an index of stability of the subtalar joint. Intra-and interobserver evaluations of measurement of this angle were performed on 20 unstable ankles. The errors at a 95 per cent confidence level were 1.9 degrees for intraobserver A, 1.4 degrees for intraobserver B and 2 degrees in interobservation. Stability of the subtalar joint was evaluated on 46 lateral ligament injuries of the ankle (23 acute injuries and 23 chronic injuries) and 80 normal ankles. The subtalar tilt angle was 9.7 degrees +/ 3.2 degrees in acute injuries 10.3 degrees #/ 2.9 degrees in chronic injuries, and 5/2 degrees +/ 2/6 degrees in normal ankles. There were significant differences between the acute or chronic injury and the normal ankles. These results suggested that stability of the subtalar joint was disturbed following acute and chronic lateral ligament injuries of the ankle.

Significance of the single-legged hop test to the anterior cruciate ligament-reconstructed knee in relation to muscle strength and anterior laxity

We investigated the significance of the single-legged hop test to the anterior cruciate ligament-reconstructed knee as it specifically relates to knee muscle strength recovery and residual anterior laxity. The hop test was conducted on 107 patients with unilateral anterior cruciate ligament-reconstructed knees (78 semitendinosus tendon autografts and 29 bone-patellar tendon-bone autografts). Patients were tested an average of 2 years after surgery. Correlation coefficient analyses determined whether the relationship between knee muscle strength recovery and the hop test was invariant across all levels of residual anterior laxity and whether the relationship between residual anterior laxity and the hop test was invariant across levels of quadriceps muscle strength recovery. Furthermore, we examined the effect of graft harvest site on the hop index. Positive correlations were found between the hop index and muscle strength index at all levels of residual anterior laxity (P < 0.05), but these correlation coefficients were relatively low. There were no apparent correlations between the hop index and residual anterior laxity at all levels of quadriceps muscle strength recovery. There was no significant difference in the average hop index between the semitendinosus tendon autograft group and the bone-patellar tendon-bone autograft group.

Studies on the mechanism of synergistic action with synergisidin and imidazole antimycotics

The investigation of mechanism of synergistic action with SYN and ECZ was performed using C. albicans SC5314 so that SYN was confirmed to show strong synergistic effects against Candida sp. in particular with addition of extremely small quantities under the MICs of imidazole antimycotics such as ECZ, MCZ and CTZ. The synergistic effect of antifungal activity against C. albicans SC5314 with a combination of SYN and ECZ (SYN + ECZ) showed fungistatic action. Effect of SYN + ECZ on osmotic resistance was not recognized and protoplast was not observed under a microscope. Accordingly, SYN + ECZ was considered not to take part in cell wall synthesis directly. For effect of SYN + ECZ on release of intracellular components, slow release of 260 nm-absorbing substances was occurred, so that SYN + ECZ was seemed not to affect cytoplasmic membrane damage directly. Also, it was suggested clearly that SYN + ECZ affected lipid metabolism and glycolysis including TCA cycle from the investigation on antagonism by growth recovery of C. albicans SC5314 by 106 kinds of substances such as fatty acids, isoprenoids, phospholipids, vitamins, amino acids, nucleic acid-related substances and TCA cycle-related substances. From the above results, it was suggested that the mechanism of synergistic action with SYN and ECZ against C. albicans SC5314 was due to affect the different reactions in lipid metabolism and the similar reactions in glycolysis including TCA cycle, respectively, in consideration of respective mechanism of actions of SYN alone and ECZ alone. A part of this work was presented at the Annual Meeting of the Agricultural Chemical Society of Japan, 1981 (Kyoto).

Studies on synergisidin

Penicillium sp. No. Y-11930 was isolated from soil sample collected at Shimouma, Setagaya, Tokyo in September 1978. Synergisidin produced by the strain was obtained with high yield in starch-corn steep liquor medium, extracted with ethyl acetate at pH 5.0 and crystallized from ethyl acetate after decolorization with active charcoal. The antibacterial activities of synergisidin against Gram-positive and Gram-negative bacteria and Mycobacterium were almost nothing but synergisidin showed weak activities against eumycetes with MICs of 6.25-100 microgram/ml. However, synergidisin was confirmed and discovered to show 30-125-fold strong synergistic effects against Candida sp. in particular with addition to extremely small quantities of imidazole antimycotics such as econazole, miconazole and clotrimazole. The acute toxicity was LD50 smaller than or equal to 250 mg/kg in mice (i.p.). the morphological degenerative effect on HeLA cells was observed in concentrations of more than 0.122 microgram/ml. The chemical structure of synergisidin was estimated as 7, 16-dihydroxy-2-methyl-4-oxo-3-oxabicyclo [10. 3. 1] hexadeca-5, 10-diene or 2, 15-dihydroxy-7-methyl-5-oxo-6-oxabicyclo (11. 3. 0] hexadeca-3, 11-diene (the same structure as decumbin, brefeldin A and ascotoxin) from various physiochemical properties but later, comparison with brefeldin A and ascotoxin revealed that synergisidin was identical with those.

Studies on terreic acid

It was found that Aspergillus sp. No. Y-8980 which was isolated from a soil sample collected at Yoron Island in Kagoshima Prefecture belonged to Aspergillus terreus group by morphological observation. The active substance produced by the strain was obtained with a high yield in sucrose-yeast extract medium and extracted by chloroform, ethyl acetate and n-butanol at pH 2.4 approximately 2.6 from the culture broth. The substance was crystallized from chloroform and ethyl acetate after charcoal treatment of the crude crystal. From various physico-chemical properties, it was found that the substance was identical to terreic acid. Terreic acid showed MICs of 25 approximately 100 mcg/ml, 12.5 mcg/ml and 50 mcg/ml against Gram-positive and Gram-negative bacteria, Xanthomonas oryzae and Xanthomonas citri, respectively, but it did not control Pseudomonas, fungi and yeast. The LD50 was 75 mg/kg i.p. and i.v. in mice. With regards to the anti-tumor effect, the morphological degeneration on HeLa cells (human carcinoma cells) was observed in the concentrations of more than 6.25 mcg/ml of terreic acid. An increase of body weight of mice caused by Ehrlich ascites carcinoma cells was not definitely observed by the daily administration of 150 mcg of terreic acid per mouse for 8 consecutive days. Above showed the enough survival effect in dd mice implanted with Ehrlich ascites carcinoma cells, and the effect also was demonstrated by anatomies of mice.

A study of the native-denatured (N in equilibrium with D) transition in lysozyme. III. Effect of alteration of net charge by acetylation

Measurement of the enzymic activity and fluorescence properties showed that the gross conformation of acetylated lysozyme [EC 3.2.1.17] is very similar to that of the native enzyme. On the other hand, protease digestion, t-butyl hypochloride modification and thermal denaturation experiments performed on native, acetylated, and guanidinated lysozymes showed that acetylation caused a small but significant shift of the N in equilibrium with D transition to the right. Thus it can be concluded that charge balance in a protein plays an important role in maintaining its conformation. The difference between equilibrium and kinetic methods of monitoring protein denaturation was also clarified.

A study of the native-denatured (N in equilibrium with D) transition in lysozyme. II. Kinetic analysis of protease digestion

Kinetic analyses of the protease digestion of several chemical derivatives of lysozyme [EC 3.2.1.17] showed that only the D(denatured) state of the protein is digested and that the reaction velocity is proportional to the equilibrium constant (KD) of the N in equilibrium with D transition of the protein. Alteration of the net charge of lysozyme by acetylation caused a shift of the N in equilibrium with D transition to the right (ten-fold increase in KD compared to that of native enzyme). Both the formation of a lysozyme-inhibitor complex and the introduction of a covalent bond in the lysozyme molecule restricted the transition. The magnitude of the N in equilibrium with D transition is related to the susceptibility of lysozyme to protease digestion and it is estimated that the N in equilibrium with D transition in proteins is generally important in the intracellular catabolism of proteins.

Effects of tetraacetyl-bis-dehydroascorbic acid, a derivative of ascorbic acid, on Ehrlich cells and HeLa cells (human carcinoma cells)

Derivatives of ascorbic acid were synthesized, and the studies were made on their effects in Ehrlich ascites carcinoma cells, in regard to the inhibition and the prolongation of survival time as well as on the morphological degeneration in HeLa cells. In a model infection study carried out by using tetraacetyl-bis-dehydroascorbic acid in dd mice infected with Ehrlich cells, it was proved that the prolongation of survival time was nearly double in comparison to the control group mice. Also, it was noted that hypertrophy due to abdominal dropsy and body weight were reduced much more than in the control group. From these results, the inhibiting effect of tetraacetyl-bis-dehydroascorbic acid was confirmed. While in the case of DHA and other derivatives, almost no inhibition and prolongation of survival time were observed. As for HeLa cells in a tissue culture, tetraacetyl-bis-DHA, in a dosage of 125-250 mug/ml, demonstrated definitely its morphological degeration. After 125 mug/ml of tetraacetyl-bis-DHA was added to a tissue culture solution of HeLa cells, the cells were washed and recultured. No growth of the cells was observed. Consequently, this substance was confirmed to be anti-HeLa substance with a low toxicity.