Small intestine histopathology. (a): Poorly differentiated adenocarcinoma composed of malignant glands (bottom, right) and diffusely distributed cancer cells (top, left). (b): Low power magnification of small intestine mucosa showing two separate spindle cell nodules in the deep mucosa. (c): Higher magnification of a spindle cell nodule shows bland cytological features of the tumor cells. (d): Immunostaining for desmin highlights the lamina muscularis mucosae as well as approximately half of the tumor cells. (e): Immunostaining of the same area for s100 decorates nerve fibres in the submucosa as well as the rest of the tumor cells.