Vanishing Act: A Case Report of Missing Breast Tumour Marker.

Breast tissue markers are essential in localising tumours post-neoadjuvant chemotherapy prior to breast-conserving surgery. However, due to the advancement in neoadjuvant therapies, greater efficacy in reducing tumour size increases the possibility of marker migration, potentially compromising surgical outcomes. We report a case of a 34-year-old woman with left breast invasive carcinoma, where the tissue marker, placed under ultrasound guidance before chemotherapy, migrated and was undetectable after eight chemotherapy cycles. The delay in surgery was resolved by identifying the marker in the left pectoral muscle using CT, though proximity to the lung prevented hook wire placement. Proposed migration mechanisms include the "accordion effect" and haematoma-induced displacement, highlighting the dynamic nature of breast tissue. Various imaging modalities, such as mammography, ultrasound, and CT, have proven helpful for marker localisation. This case underscores the need for a deeper understanding of tissue dynamics and emphasises interdisciplinary communication to adapt treatment strategies. As medical knowledge continues to evolve, insights are needed to refine best practices in breast cancer management and radiological interventions.