Figure 1

Histochemical staining of frozen sections of an intraperitoneal primary mouse plasma cell tumor. A nodule rich in plasma cells can be seen in the midst of surrounding stromal and fat cells. The stains of the sections are as follows: H&E, hematoxylin and eosin; Nissl; MGP (methyl green pyronin) and kappa (immunoperoxidase in the top four panels or immunofluorescence in the bottom four panels) staining of immunoglobulin kappa light chains). The images in the top four panels represent frozen sections stained and mounted under cover slips in a distant histology laboratory and captured using high quality optics in a photographic studio. Those in the bottom four panels reflect the challenges of interpreting microscopic views on a microscope optimized for LCM, viewing frozen sections that had been processed and stained with the utmost speed to minimize RNA damage and lacking cover slips. Ovals indicate clusters of plasma cells with characteristic MGP staining and rich in Ig κ protein.