Which stain is positive in the histology of lung adenocarcinoma?

Lung adenocarcinoma typically shows positive staining with the Periodic Acid-Schiff (PAS) stain due to its ability to highlight carbohydrates, specifically mucin. Adenocarcinomas, especially those in the lung, often produce mucin, and the presence of this mucin-rich matrix can be effectively visualized with the PAS stain. The stain reacts with the polysaccharides present in mucin, leading to a magenta coloration that indicates the presence of this component.

The other staining techniques mentioned serve different purposes. Hematoxylin and eosin is a routine stain used to analyze general tissue architecture and cellular details but does not specifically highlight mucin. Gram stain is primarily utilized to identify bacterial pathogens and is not appropriate for diagnosing tumors. Silver stain is commonly used for certain types of fungi, reticular fibers, and neurofibrils, but it is not specific for adenocarcinomas and does not detect mucin effectively. Therefore, PAS is the most relevant and diagnostic stain for visualizing mucin in lung adenocarcinoma.