Dendritic cells (DCs) are central to anti‑tumour immunity, yet their functional diversity and conservation across human cancers and disease progression remain incompletely understood. To enable high‑resolution interrogation of tumour‑associated DCs, we curated and integrated publicly available single‑cell RNA sequencing datasets to generate an atlas of human myeloid antigen‑presenting cells comprising 498,023 cells from 589 samples across 36 studies. The atlas includes approximately 30,000 DCs spanning 12 cancer types, with representation of primary tumours, metastatic lesions, and healthy tissues, enabling comparison of DC states across disease stage and tissue context. Across cancers, we identified cDC1, cDC2, and CCR7 DCs as the dominant DC populations consistently present in human tumours. While these core populations were broadly conserved, substantial heterogeneity was evident within the cDC2 compartment, varying across cancer types and further stratified by healthy tissue, primary tumour, and metastatic disease. Within the DC2 compartment, we identified previously described transcriptional states, including IL1B DC2 enriched in genes associated with an inflammatory phenotype and CD207 DC2 enriched in genes associated with a tolerogenic phenotype. Across cancer types, these DC2 states displayed systematic changes with tumour progression, with IL1B DC2 reduced with disease progression in several cancer types. In contrast CD207 DC2 were enriched in tumors associated with mucosal barriers and increased with disease progression. In ovarian cancer, these DC2 states exhibited further context‑specific diversification between primary tumours and metastatic sites, consistent with dynamic remodelling of the DC2 compartment during disease evolution. This atlas represents a valuable resource for direct comparison of dendritic cell states across healthy tissue, primary tumours, and metastases in human cancer.