Accurate phenotyping of cells in the tumor microenvironment is essential for understanding cancer biology but typically requires precise cell segmentation, limiting scalability. Here, we introduce Contrastive Learning Enabled Accurate Registration of Immune and Tumor cells (CLEAR-IT), a self-supervised framework that learns cell-level features from multiplexed images using only cell locations. CLEAR-IT encoders achieve strong linear evaluation performance, improve substantially with hyperparameter optimization, and maintain high accuracy across imaging modalities and with up to 90% fewer labels. When substituted for handcrafted features in a state-of-the-art classifier, CLEAR-IT features yield higher performance, and their combination enables comparable accuracy with less than half of the labeled data otherwise required. The learned representations also support prognostic modeling: using annotations from a single patient, CLEAR-IT-based phenotyping identifies survival-associated tissue features that generalize across two cohorts and modalities. CLEAR-IT provides a segmentation-light, label-efficient approach for scalable cell phenotyping and enhances existing workflows in digital pathology and tumor microenvironment analysis.

Forensic microtrace investigation relies on time- and labour-intensive microscopic analyses. To aid forensic experts in their investigations, an image recognition model for microtrace localisation and classification is needed. In this work, we use deep learning to automate trace recognition in images captured with automated microscopy. We localise and classify fibres, hairs, skin, glass and sand in microscopy scans through pixel-wise classification of tape-lift samples. As deep learning requires extensive amounts of annotated training data, we additionally investigate various pretraining strategies to minimise the required annotation workload. We compare ImageNet pretraining, pretraining with self-supervised learning and a sequential application of these approaches. We find that pretrained models are able to reduce the required annotated data twofold compared to models trained from scratch while retaining the prediction accuracy. While our ImageNet-pretrained models outperform our self-supervised-pretrained models, we achieve the highest accuracy by combining the two approaches, resulting in a factor 4 reduction of manual annotated microtraces or a 65 % improvement in recognition and localisation accuracy (mean intersection over union increases from 0.34 to 0.56 due to pretraining) when training on only 2.2 dm² of annotated tape lift scans. The developed models offer a solid fundament for automated analysis of forensic microtrace scans.