Churg et al. firstly described the cases of MIS with flat or slightly papillary single-layer surface mesothelial proliferation with BAP1 loss and/or CDKN2A homozygous deletion in patients with recurrent non-resolving pleural effusions and without evidence of tumor on imaging or thoracoscopy [13,14]. The gene discussed is CDKN2A; the disease is neoplasm.