a, b Conventional cytology with benign mesothelial cells surrounded by lymphocytes satellitosis of mesothelial cells by lymphocytes (a, b, ×630, Papanicolaou stain). c, d The mesothelial nature of the encircled cells from our patient at the time of the putative MPMIS was confirmed by immunocytochemistry for calretinin (c, d, ×630, immunoperoxidase).