Figure 6 (A) Alcian blue staining of epithelioid malignant mesothelioma highlights intracytoplasmic (arrowhead) and intraluminal (arrow) droplets of hyaluronic acid. (B) Staining is markedly reduced in a serial section pretreated with hyaluronidase. (C) Periodic acid‐Schiff staining of neutral mucin is unaffected by diastase digestion, as is shown in the cytoplasmic vacuoles (arrows) of this adenocarcinoma metastatic to the pleura.