Didonato R, et al. - In this study, researchers reported the largest series of invasive mucinous carcinomas (IMC) treated with Neoadjuvant chemotherapy (NAC). They report on the characteristic, but not well recognized, pattern of pathological response. Pathological assessment after NAC showed marked reduction in tumour cellularity, but persistent space-occupying mucin pools. Persistent mass-forming low-cellular or acellular mucin pools can lead to discordant clinical, imaging and pathological findings in IMC treated with NAC.