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  <front>
    <journal-meta />
    <article-meta>
      <title-group>
        <article-title>Enhancing Skin Cancer Detection Using Curriculum Learning In Ensemble Deep Learning Context</article-title>
      </title-group>
      <contrib-group>
        <contrib contrib-type="author">
          <string-name>Riadh Meghatria</string-name>
          <email>r.meghatria@univ-boumerdes.dz</email>
          <xref ref-type="aff" rid="aff0">0</xref>
        </contrib>
        <contrib contrib-type="author">
          <string-name>Djamel Gaceb</string-name>
          <email>d.gaceb@univ-boumerdes.dz</email>
          <xref ref-type="aff" rid="aff0">0</xref>
        </contrib>
        <contrib contrib-type="author">
          <string-name>Fayçal Touazi</string-name>
          <email>f.touazi@univ-boumerdes.dz</email>
          <xref ref-type="aff" rid="aff0">0</xref>
        </contrib>
        <contrib contrib-type="author">
          <string-name>Tina Boukert</string-name>
          <email>boukerttina@gmail.com</email>
          <xref ref-type="aff" rid="aff0">0</xref>
        </contrib>
        <contrib contrib-type="author">
          <string-name>Sarah Ben Aidrene</string-name>
          <email>sarahbenaidrene@gmail.com</email>
          <xref ref-type="aff" rid="aff0">0</xref>
        </contrib>
        <aff id="aff0">
          <label>0</label>
          <institution>LIMOSE laboratory, CS department, University M'hamed Bougara</institution>
          ,
          <addr-line>Boumerdes</addr-line>
          ,
          <country country="DZ">Algeria</country>
        </aff>
      </contrib-group>
      <pub-date>
        <year>2026</year>
      </pub-date>
      <abstract>
        <p>Accurate classification of skin lesions, particularly for melanoma detection, remains a critical challenge in medical image analysis. Leveraging recent advances in deep learning, this paper investigates the use of curriculum learning in ensemble deep learning context for melanoma classification. To validate the proposition, three primary strategies are compared: transfer learning of CNNs using VGG16, ResNet50, and EficientNetB0 models; ensemble learning techniques such as bagging; and curriculum learning that progressively guides training in increasing order of complexity. Experiments conducted on the ISIC 2019 and 2020 dermoscopic image datasets demonstrate that curriculum learning applied to EficientNetB0 achieves superior classification performance, reaching an F1- score of 90.77%, outperforming conventional fine-tuning and ensemble approaches. These results underscore the potential of integrating curriculum learning in ensemble learning context with state-of-the-art CNN architectures to improve the robustness and accuracy of automated melanoma diagnosis.</p>
      </abstract>
      <kwd-group>
        <kwd>eol&gt;Skin Lesions</kwd>
        <kwd>Melanoma Detection</kwd>
        <kwd>Deep Transfer Learning</kwd>
        <kwd>Ensemble Deep Learning</kwd>
        <kwd>Medical Image Analysis</kwd>
        <kwd>Medical Diagnosis</kwd>
        <kwd>Curriculum Learning</kwd>
      </kwd-group>
    </article-meta>
  </front>
  <body>
    <sec id="sec-1">
      <title>1. Introduction</title>
      <p>
        The accurate and early diagnosis of skin cancer, particularly melanoma, is a critical public health
challenge due to its aggressive nature and potential for metastasis if undetected. Traditional manual
interpretation of dermatological images by clinicians is a complex, time-consuming task prone to
inter-observer variability, misdiagnosis, or delayed treatment [
        <xref ref-type="bibr" rid="ref1">1</xref>
        ]. This inherent dificulty arises from
the subtle visual similarities between benign and malignant lesions, significant intra-class variability,
and the presence of confounding image artifacts. Consequently, there is an urgent need for robust,
automated diagnostic tools to augment clinical decision-making.
      </p>
      <p>
        Artificial Intelligence (AI), and specifically deep learning (DL), has emerged as a transformative force
in medical imaging, ofering unprecedented opportunities to enhance diagnostic eficiency and accuracy
[
        <xref ref-type="bibr" rid="ref2">2</xref>
        ]. Deep Convolutional Neural Networks (CNNs) have demonstrated state-of-the-art performance
across numerous medical image analysis tasks, including detection, segmentation, and classification [
        <xref ref-type="bibr" rid="ref3">3</xref>
        ].
Their remarkable ability to automatically learn hierarchical, discriminative features directly from raw
image data spares the labor-intensive process of manual feature engineering, making them particularly
well-suited for intricate diagnostic problems like skin lesion classification [
        <xref ref-type="bibr" rid="ref4">4</xref>
        ]. Furthermore, transfer
learning (TL), which involves fine-tuning or reusing features from models pre-trained on large-scale
datasets such as ImageNet, has proven highly efective in medical contexts where annotated datasets are
typically scarce [5]. Architectures like VGG16, ResNet50, InceptionV3, EficientNetB0, and Xception have
been widely adopted through TL to achieve commendable performance in dermatological applications.
      </p>
      <p>Despite these advancements, several challenges persist in deploying DL models for reliable clinical
diagnosis. Models frequently struggle with pronounced class imbalance in medical datasets, high
intraand inter-class variability of lesions, and the presence of ambiguous or atypical cases that lead to
uncertain predictions [6]. While ensemble learning methods [7], which aggregate predictions from
multiple models, can mitigate these issues by improving predictive stability and leveraging model
diversity [8], they do not address the fundamental learning process on challenging samples. To foster
more robust representation learning and address diagnostic uncertainty, curriculum learning (CL) has
attracted increasing attention [9]. Inspired by human cognitive development, CL involves structuring
the training process by progressively introducing data samples from simple to complex, thereby guiding
the model’s optimization and enhancing its generalization capabilities [10].</p>
      <p>This work systematically investigates advanced deep learning strategies to enhance the automated
classification of skin lesions, with a particular emphasis on demonstrating the eficiency of curriculum
learning in this challenging domain. Our core objective is to show that a confidence-based curriculum
used in ensemble deep learning context, when applied to powerful pre-trained CNNs, can surpass
the performance of both conventional TL and ensemble methods for melanoma detection. The main
contributions of this paper are summarized as follows:
• A comprehensive empirical evaluation of five pre-trained CNN architectures (VGG16, ResNet50,
InceptionV3, EficientNetB0, and Xception) under two distinct transfer learning modes: feature
extraction and fine-tuning.
• The implementation and assessment of a bagging-based ensemble approach applied to the
EficientNetB0 architecture, designed to enhance predictive stability and robustness for skin lesion
classification.
• The development of a novel curriculum-learning framework in ensemble deep learning context,
where training data is dynamically ordered by diagnostic dificulty (derived from initial classifier
confidence), enabling a progressive and more efective model adaptation process.
• A rigorous experimental study conducted on a two-class dataset derived from the ISIC 2019 and
ISIC 2020 challenges, providing a robust benchmark for binary classification of melanoma versus
nevus.</p>
      <p>The remainder of this paper is structured as follows: Section 2 provides an overview of related work in
automated skin lesion classification. Details of the proposed methods are then provided in section 3,
including the transfer learning strategies, the ensemble approach, and the curriculum learning approach
applied in ensemble deep learning context. In section 4, the experimental results are presented and
discussed, comparing the performance of all implemented approaches. Finally, Section 5 concludes the
paper and outlines promising directions for future research.</p>
    </sec>
    <sec id="sec-2">
      <title>2. Related Work</title>
      <p>In line with numerous research fields and applications influenced by AI revolution over the past decade,
the automatic detection and classification of skin cancer from medical images has also witnessed
significant advancements. In this context, several automated systems using AI models and techniques
have been introduced to facilitate early non-invasive diagnosis. This section provides a review of prior
work and existing methodologies for skin cancer detection and classification, spanning from traditional
machine learning techniques to state-of-the-art deep learning and ensemble approaches, highlighting
their evolution, key contributions, and limitations.</p>
      <sec id="sec-2-1">
        <title>2.1. Machine Learning Approaches</title>
        <p>Early eforts in automated skin cancer detection primarily used traditional machine learning algorithms,
which typically relied on handcrafted features (such as texture, color, and shape descriptors) extracted
from images, followed by classification (like SVM, KNN, and decision trees). While providing preliminary
solutions, their main limitation was the inability to automatically capture the complex discriminative
features inherent in dermatoscopic images, often requiring tedious expert intervention.</p>
        <p>An early work by Codella et al. (2015) [11] proposed a method that combined deep learning with
sparse coding and SVM for melanoma recognition. Aiming to reduce the reliance on extensive annotated
data, the authors tried to benefit from unsupervised learning and transferring features from natural
photographs, mimicking expert clinical reasoning. Evaluated on 2,624 clinical cases, their method
achieved 93.1% precision for distinguishing melanoma from non-melanoma lesions. More recently,
Wei et al. (2024) [12] explored the eficacy of classical machine learning algorithms for early skin
cancer detection. They applied SVM, KNN, and Decision Tree algorithms on a large ISIC dataset
(53,177 images across seven classes). Their results indicated that KNN achieved the highest multiclass
precision at 74.93%, while SVM ofered better binary classification with an AUC of 0.676. Despite their
interpretability and lower computational demands, these methods often require expert-driven feature
engineering and struggle to capture complex image patterns, limiting their diagnostic accuracy and
scalability. Consequently, these approaches remain valuable as baseline references but are increasingly
being outperformed by deep learning models capable of autonomously learning highly discriminative
features.</p>
      </sec>
      <sec id="sec-2-2">
        <title>2.2. Deep Learning Approaches</title>
        <p>
          The significant potential of CNNs was underscored by Esteva et al (2017) [
          <xref ref-type="bibr" rid="ref4">4</xref>
          ] who demonstrated that
these models could achieve classification capabilities comparable to expert dermatologists. Utilizing a
dataset of 129,450 clinical and dermoscopic images, their approach employed a GoogLeNet Inception v3
model with transfer learning, reaching 72.1% of precision in disease classification and showing superior
performance in specific test cases involving carcinoma, melanoma, and dermoscopy. Following this,
Demir et al. (2019) [13] evaluated the performance of two prominent deep CNN architectures,
ResNet101 and Inception-v3, for binary (benign/malignant) skin cancer diagnosis. Their study, conducted on
an ISIC-based dataset, reported that Inception-v3 achieved 87.42% precision, slightly outperforming
ResNet-101 (84.09%). Expanding on the utility of transfer learning, Laith Alzubaidi et al. (2021)[5]
proposed leveraging deep neural network models to enhance skin cancer detection. Their hybrid
DCNN model, trained on the HAM10000 dataset, attained a high precision of 98.53% and an F1-score of
89.09%, demonstrating the efectiveness of data augmentation in improving model performance. Further,
Aljohani and Turki (2022) [14] conducted a comparative study of eight diferent CNN architectures,
including DenseNet201, MobileNetV2, ResNet50V2, and GoogleNet, for binary melanoma classification
using the ISIC 2019 dataset. GoogleNet exhibited the best test performance with a precision of 76.08%,
highlighting the varying efectiveness of diferent established CNN architectures. These CNN-based
methods significantly outperform traditional machine learning by capturing hierarchical image features
but often require large annotated datasets and substantial computational resources. Moreover, despite
these improvements, standard CNNs efectiveness can sometimes be limited by their ability to capture
global contextual information and subtle features in complex dermatoscopic images.
        </p>
      </sec>
      <sec id="sec-2-3">
        <title>2.3. Enhanced and Hybrid Architectures Approaches</title>
        <p>
          To address the limitations of standard CNNs, researchers have introduced some enhanced and hybrid
deep learning architectures. These models often combine the strengths of diferent network types or
incorporate task-specific mechanisms. Catal Reis et al. (2022) [ 15] introduced InSiNet, a CNN adapted
for skin cancer classification, achieving up to 94.59% precision on ISIC datasets and outperforming
conventional deep learning and traditional machine learning methods. In a comparable way, Shah et
al. (2024) [16] integrated explainable AI with Xception for early melanoma detection, attaining 98.5%
precision on ISIC 2018 and enhancing interpretability via Grad-CAM and LIME. Building on the idea of
specialized components, Kavitha et al. (2024)[
          <xref ref-type="bibr" rid="ref3">3</xref>
          ] proposed a CNN-R-CNN hybrid approach for multi-class
classification of nine skin cancer types, combining preprocessing and data augmentation to reach 91.32%
of precision and 76,92% of F1-score on ISIC images. More advanced hybrid models, such as MetaFormer
introduced by Pacal et al. (2025)[17], merging CNNs with Vision Transformers (ViT) to leverage
both local feature extraction and global contextual understanding. MetaFormer, featuring a Focal
Self-Attention mechanism, delivered remarkable performance with 92.54% of precision on ISIC 2019
and 95.01% on HAM10000, while maintaining a low parameter count for mobile deployment. Similarly,
Ozdemir and Pacal (2025) [10] developed an innovative hybrid deep learning model for multiclass skin
cancer classification, integrating ConvNeXtV2 blocks with separable attention mechanisms. Trained on
ISIC 2019, this model achieved 93.48% of precision and 91.82% of F1-score, surpassing many existing
CNN and ViT-based models. Despite their accuracy gains by capturing complex features, such hybrid
architectures, often increase computational demands and pose interpretability challenges.
        </p>
      </sec>
      <sec id="sec-2-4">
        <title>2.4. Ensemble Methods and Advanced Optimization</title>
        <p>To address issues like model bias, variance, and limited generalizability, ensemble methods were explored
where predictions of multiple individual models aggregated to produce a more robust and accurate
ifnal decision. These techniques frequently outperforming any single model. In fact, numerous studies,
in the context of medical image classification, have demonstrated the eficiency of such techniques.
For instance, Khaled et al. (2023) [18] proposed a stacking framework that combines multiple CNN
architectures to improve classification accuracy across diverse medical imaging modalities and
anatomical regions. In a related efort, for brain lesion detection, Laribi et al. (2024) [ 19] demonstrated that
ensembles combining CNNs and ViTs achieved significant improvements. More recently, Khaled et
al. (2025) [20] integrated progressive transfer learning with ensemble methods to achieve significant
enhancements in mammogram-based breast cancer diagnosis. In the context of skin lesion analysis,
ensembles techniques have likewise shown strong potential. Rahman et al. (2021) [21] demonstrated
substantial gains, improving recall to 94% by aggregating five diverse CNN architectures on HAM10000
and ISIC datasets for classifying seven types of skin lesions. Bassel et al. (2022) [22] extended this
with multi-level stacking of CNN-derived features and traditional classifiers (SVM, Random Forest,
KNN, and logistic regression). This yielded 90.9% precision and F1-score, highlighting the benefit of
cross-paradigm integration, albeit at increased computational cost. Moreover, subsequent work has
focused on enhancing ensemble pipelines through data enrichment and optimization. Chang et al.
(2022)[23] combined MELA-CNN image features with clinical metadata (age, sex) and applied K-means
SMOTE to address class imbalance, achieving an F1-score of 86.1% and an AUC of 0.970 with XGBoost.
Shortly after, Thanka et al. (2023)[24] integrated VGG16-based features with XGBoost and LightGBM
classifiers, leveraging GAN-generated synthetic samples to balance the ISIC data and reach 99.1%
of precision and 99.4% of recall, though reliance on synthetic data may risk overfitting. Natha et al.
(2024)[25] further advanced ensemble strategies by combining Max Voting across pre-trained ensemble
models (Random Forest, Gradient Boosting) with Genetic Algorithm-based feature selection, achieving
95.80% of precision and 95.20% of F1-score on ISIC 2018 and HAM10000, while reducing overfitting and
improving generalization. Ghosh et al. (2024)[8] extended the feature diversity concept by combining
deep learning embeddings from VGG-19, Capsule Network, and ViT with multiple machine learning
classifiers through majority voting, achieving 91.6% precision. In addition, Gamil et al. (2024) [ 26]
integrated EficientNet-B0 features with PCA and an AdaBoost and SVM ensemble, attaining 93% precision
on DermIS and 91% on ISIC, indicating strong diagnostic potential despite persistent interpretability
challenges. While ensemble methods significantly boost robustness and accuracy, they often come
with increased computational complexity and can reduce the overall interpretability of the diagnostic
decision.</p>
      </sec>
    </sec>
    <sec id="sec-3">
      <title>3. Methodology</title>
      <p>In this work, we investigate a range of deep learning strategies for the binary classification of skin
lesions, specifically diferentiating melanoma from nevus. The methodological framework is designed
to enhance both predictive accuracy and model robustness, leveraging advanced CNN architectures
and contemporary training paradigms. For this, we structured the study around three approaches: (i)
transfer learning, (ii) ensemble deep learning via bagging, and (iii) curriculum learning used in ensemble
deep learning context. A comprehensive description of the dataset is first provided, followed by a
detailed explanation of each proposed approach.</p>
      <sec id="sec-3-1">
        <title>3.1. Dataset Description</title>
        <p>Our experiments were conducted on the ISIC 2019 and 2020 Melanoma Dataset [27], a fusion of the
ISIC 2019 [28, 29, 30] and ISIC 2020 [31] challenges. The ISIC 2019 comprises over 25,000 dermoscopic
images across nine lesion categories, including 4,522 melanoma cases, while the ISIC 2020 dataset
contains 33,126 images across two classes with only 584 melanoma cases. For our study, only two
diagnostic categories of high clinical relevance were considered, namely melanoma (MEL) and nevus
(NV) resulting in 11.449 images (5,106 MEL, 6,343 NV). To mitigate class imbalance, we applied random
under-sampling of the majority class. Figure 1 presents representative example images from each class.</p>
      </sec>
      <sec id="sec-3-2">
        <title>3.2. Transfer Learning Approach</title>
        <p>Given their documented success in medical image analysis, five CNN architectures (VGG16, InceptionV3,
Xception, ResNet50, and EficientNetB0) were employed as backbone models in this approach. To
leverage the advantages of transfer learning, each model was initialized with weights pre-trained on the
ImageNet dataset. Two transfer learning strategies were explored, resulting in two distinct experimental
scenarios for this approach: feature extraction and fine-tuning.</p>
        <p>In the feature extraction scenario, as illustrated in Figure 2, the convolutional backbone was frozen,
and only the classification layers were trained, thereby utilizing the pretrained weights exclusively for
feature representation while adapting the classifier to the target task. Conversely, in the fine-tuning
scenario (illustrated in figure 3), a subset of the upper convolutional layers was unfrozen and jointly
optimized with the classification head, enabling the adaptation of high-level feature representations to
the specific characteristics of the dermatological domain. This approach seeks to achieve an optimal
trade-of between the generalization benefits of pretrained representations and the specialization
required for accurate skin lesion classification.</p>
        <p>Convolution Backbone (example: VGG16)
56 x 56 x 256
28 x 28 x 512</p>
      </sec>
      <sec id="sec-3-3">
        <title>3.3. Ensemble Learning Approach</title>
        <p>In this approach, Ensemble methods were explored. To enhance predictive robustness and reduce
variance, we employed an ensemble learning strategy based on bootstrap aggregating (bagging) using
multiple EficientNetB0 models. In this framework, multiple instances of EficientNetB0 are each trained
(fine-tuned) on distinct bootstrap-resampled subsets of the original training set, ensuring diversity
among base learners. During inference, predictions from all trained models are combined through
majority voting to yield the final classification output. The detailed procedural steps of this approach
are outlined in Algorithm 1.</p>
        <sec id="sec-3-3-1">
          <title>Algorithm 1 Bagging with EficientNetB0 Base Learners</title>
          <p>Input: Training dataset  = {(train, train)},
number of ensemble members  ,
base model  (EficientNetB0)
Output: Final prediction ^</p>
          <p>Initialization:
// set of trained base models</p>
        </sec>
      </sec>
      <sec id="sec-3-4">
        <title>3.4. Curriculum Learning Approach</title>
        <p>Inspired by human pedagogy or learning behavior, the curriculum learning (CL) process begins by
relying on simpler samples and progresses to more complex data to improve generalization, reduce
sensitivity to noisy or ambiguous samples, and facilitate more stable convergence.</p>
        <p>In this approach, we propose a curriculum-learning pipeline that leverages the EficientNetB0 model
as a backbone to be fine-tuned, due to its favorable trade-of between accuracy and computational
eficiency. The following steps detail the process of this approach (visualized in figure 4), starting from
ranking the samples by dificulty to the final validation phase:
3.4.1. Dificulty-Based Ranking
This stage aims to identify and rank skin lesion images according to their diagnostic complexity. The
output of this step is an ordered dataset, starting with the most straightforward cases (characterized
by distinct morphological patterns, absence of artifacts, and minimal noise) and progressing to the
most challenging cases, involving subtle lesion features, imaging artifacts, or significant anatomical
variability. This ordered structure is obtained by leveraging the confidence scores produced by the
model’s softmax activation, which serve as a quantitative measure of predictive certainty, thereby
enabling a systematic and reproducible arrangement of images from easiest to most dificult.
3.4.2. Progressive Curriculum Construction
To allow for a gradual learning, we need to partition the ordered dataset into subsets, each corresponding
to a level of dificulty, which will be used to train the model gradually or progressively. Each image is
thus associated with a certainty level derived from the predicted probability of its ground-truth label.
In our approach, we chose to partition the training set into five such dificulty levels, defined in Table 1:
3.4.3. Training phase
The training process begins with the least complex images, enabling the model to acquire fundamental
visual representations and recognize clear diagnostic patterns. Performance is then periodically assessed
on a validation set, enabling the refinement of model parameters before progressing to succeeding
higher-complexity cases. Subsequently, increasingly challenging images are introduced in a progressive
manner by training on added complexity level subsets and validating accordingly. This allows the
model to incrementally enhance its feature representations and improve its ability to address atypical
or ambiguous cases.
3.4.4. Final consolidation across the entire dataset
After completing or running over all complexity levels, the model is trained on the full training dataset
to solidify learned representations and reinforce its generalization capability.
3.4.5. Final validation on an independent test set
Finally, for a rigorous assessment of its robustness and diagnostic accuracy. The model is evaluated on
an unseen dataset (test set) that reflects real-world clinical scenarios.</p>
        <p>BAG 1
BAG 2
BAG 3
BAG 4
BAG 5</p>
      </sec>
      <sec id="sec-3-5">
        <title>3.5. Advanced Optimization</title>
        <p>Our experiments involved training and evaluating five ImageNet-pretrained CNN backbones (VGG16,
InceptionV3, Xception, ResNet50, and EficientNetB0) using diferent training strategies on a balanced
subset of the ISIC 2019 and ISIC 2020 datasets. To enhance generalization and mitigate overfitting,
we applied data augmentation techniques including random flips, brightness/contrast/saturation
adjustments, and random crops, alongside stratified train/validation/test splits. Models were trained for
25 epochs with an early stopping patience of 5, and curriculum learning was employed by gradually
progressing through five dificulty levels before consolidation on the full dataset. Performance was
evaluated using Accuracy, Precision, Recall, and F1-score. Typically, the F1-score is the performance
indicator of choice when it comes to comparative evaluations of multiple approaches in medical data
analysis, as this clinical context is particularly sensitive to false positives and false negatives. For this
reason, the F1-score was adopted as the primary metric in our study.</p>
      </sec>
    </sec>
    <sec id="sec-4">
      <title>4. Results</title>
      <p>As outlined before, we evaluated three deep learning approaches for the binary classification of skin
lesions, distinguishing melanoma from nevus on a combined dataset from ISIC 2019 and ISIC 2020. The
results of these evaluations are presented in the following subsections.</p>
      <sec id="sec-4-1">
        <title>4.1. Transfer Learning Approach</title>
        <p>In this approach, we trained and evaluated five CNN architecture (InceptionV3, Xception, VGG16,
ResNet50, and EficientNetB0) applied under transfer learning paradigms, both as feature extractors
(scenario1) and with fine-tuning (scenario 2). Initial experiments of Scenario 1 where transfer learning
was applied with frozen convolutional layers revealed varied performance across the diferent CNN
architectures. ResNet50 and EficientNetB0 achieved the highest F1-scores among the models, as
illustrated in Table 2, with ResNet50 reaching an F1-score of 88.79% and EficientNetB0 closely following
at 88.66% . VGG16 also performed competitively with an F1-score of 87.07%, while InceptionV3 and
Xception lagged behind with scores of 81.60% and 84.55%, respectively. These results indicate that
the architectures, such as EficientNetB0 and ResNet50, are better suited for capturing discriminative
features in dermoscopic images.</p>
      </sec>
      <sec id="sec-4-2">
        <title>4.2. Ensemble Learning Strategies Approach</title>
        <p>To improve robustness and reduce variance, we implemented ensemble learning using bagging with
EficientNetB0 as the base learner. The ensemble aggregated predictions from multiple independently
trained instances of EficientNetB0 models. This approach yielded consistent improvement achieving
an F1-score of 88.86% as reported in Table 4.</p>
      </sec>
      <sec id="sec-4-3">
        <title>4.3. Curriculum Learning Approach</title>
        <p>The most significant performance gains were observed when applying curriculum-learning strategy
combined with fine-tuned EficientNetB0 model. Curriculum learning involved structuring the training
process to present images in increasing order of complexity, allowing the model to progressively learn
from simpler to more challenging examples. This approach led to a marked improvement in classification
metrics, with EficientNetB0 achieving an F1-score of 90.77%, as listed in Table 5, surpassing both the
single-model transfer learning and ensemble bagging approaches.</p>
      </sec>
    </sec>
    <sec id="sec-5">
      <title>5. Discussion</title>
      <p>The results of this study highlight the significant benefits of applying curriculum learning strategy for
the classification of skin lesions using deep convolutional neural networks, particularly EficientNetB0.
Curriculum learning, by organizing training samples from easier to harder based on a confidence-derived
dificulty metric, appears to facilitate a more efective learning process. This progressive exposure
enables the model to first capture robust feature representations from clear, unambiguous examples
before adapting to more challenging, noisy images. Such a training strategy likely contributes to
improved convergence stability and ultimately yielded a higher F1-score (90.77%) compared to other
approaches. Furthermore, the curriculum learning method not only improved the F1-score but also
enhanced precision and recall, reaching 93.74% and 87.99%, respectively, indicating a better balance
between false positives and false negatives, which is critical in clinical contexts . This suggests that
curriculum learning efectively guides the model to better generalize by focusing on easier samples
ifrst, thereby stabilizing the learning process and reducing misclassification rates. On the other hand,
the ensemble learning via bagging revealed complementary strengths compared to curriculum learning,
evidenced by an F1-score of 88.86% for EficientNetB0 ensembles, highlighting the validity of this
approach in reducing the variance of the predictions and improving robustness of the model. As
well, regarding transfer learning approaches, fine-tuning enhanced performance across most CNN
models compared to pure feature extraction, with notable gains observed for VGG16. This aligns with
existing literature emphasizing the importance of adapting pretrained weights to domain-specific data
for improved representation learning. Nonetheless, curriculum learning surpassed fine-tuning alone,
delivering the largest absolute improvement in classification performance within this experimental
framework. In summary, the integration of curriculum learning into the training pipeline for skin lesion
classification ofers a robust and eficient means to improve model accuracy and stability beyond
traditional transfer learning and ensemble methods. These findings underscore the value of incorporating
data-driven sample dificulty ordering in deep learning workflows, particularly in medical domains
where data complexity and variability pose significant challenges. Future work should explore the
generalizability of curriculum learning across diverse datasets and investigate its synergy with other
advanced techniques and modalities to further enhance clinical applicability.</p>
    </sec>
    <sec id="sec-6">
      <title>6. Conclusion</title>
      <p>This work presented a comparative study of transfer learning, ensemble deep learning, and curriculum
learning strategies for melanoma classification from dermoscopic and clinical images. Our findings
confirm the efectiveness of deep CNNs in skin lesion analysis and provide evidence that curriculum
learning ofers tangible advantages over conventional or even ensemble methods. By gradually exposing
models to increasingly dificult samples, curriculum learning used in ensemble deep learning context
improves feature refinement and enhances robustness when faced with atypical or ambiguous lesions.
Beyond performance gains, curriculum learning contributes to better generalization, an essential
property for clinical deployment where unseen cases may deviate significantly from training data. The
integration of such progressive training schemes into automated diagnosis systems could therefore
support dermatologists with more reliable and eficient decision-making. Future work will focus on
expanding curriculum design by incorporating alternative dificulty measures, such as low-level image
quality indicators or complexity metrics derived from auxiliary models. Additionally, evaluating the
approach across larger and more heterogeneous datasets will be critical to validate its applicability in
real-world clinical environments.</p>
    </sec>
    <sec id="sec-7">
      <title>Declaration on Generative AI</title>
      <sec id="sec-7-1">
        <title>The author(s) have not employed any Generative AI tools.</title>
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