Mucosal biopsy findings. (A) Biopsy of the gastric antrum shows diffuse infiltration of the lamina propria by the atypical cells. The muscularis mucosa is intact, without infiltration of the submucosa. (B) A CD56 stain of the same biopsy highlights the atypical infiltrate. Photomicrographic images were acquired with a Nikon Eclipse 50i microscope equipped with an Olympus DP71 camera and software. Final image preparation was performed with Adobe Photoshop CS3 extended Version 10.0.1. Magnification: 2×/0.1 NA Plan Apo lens.