Our previous work on experimental mouse models of MPE revealed that pleural tumour-secreted C–C motif chemokine ligand 2 (CCL2) mediates MPE formation by stimulating angiogenesis and vascular leakage and by driving myeloid cells, including monocytes and mast cells, from the bone marrow to the pleural metastatic milieu5, 6, 7. Here, CCL2 is linked to pleural neoplasm.