End-to-End Ugly Duckling Sign Detection for Melanoma Identification with Transformers

The concept of ugly ducklings was introduced in dermatology to improve the likelihood of detecting melanoma by comparing a suspicious lesion against its surrounding lesions. The ugly duckling sign suggests nevi in the same individual tend to resemble one another while malignant melanoma often deviates from this nevus pattern. Differentiating the ugly duckling sign was more discriminatory between malignant melanoma and other nevi than quantitatively assessing dermoscopic patterns. In this study, we propose a framework for modeling ugly duckling context in melanoma identification (called UDTR hereafter). To this end, we construct our model in three parts: Firstly, we extract multi-scale features using a deep neural network from lesions in the same individuals; Then, we learn lesion context by modeling the dependency among features of lesions using a transformer encoder; Finally, we design a two branch architecture for performing both patient-level prediction and lesion-level prediction concurrently. Also, we propose a group contrastive learning strategy to enforce a large margin between benign and malignant lesions in feature space for better contextual feature learning. We evaluate our method on ISIC 2020 dataset which consists of similar to 30,000 images from similar to 2,000 patients. Extensive experiments evidence the effectiveness of our approach and highlight the importance of detecting lesions with clues from surrounding lesions than that of only evaluating lesion in question.