Normal colonic mucosa can mimic prostate adenocarcinoma morphologically with rows of small glands with cells with large nuclei, prominent nucleoli, and amphophilic cytoplasm. Note that they lack goblet cells due to procedural compression. These glands stain like prostate cancer with a triple stain (PIN4), showing diffuse staining for arginase (red) and lack of staining for p63 and HMWCK. The key to avoiding this morphological and immunohistochemical pitfall is to identify the lamina propria (arrow) surrounding the colonic glands. Additionally, positive CDX2 immunostaining confirms the intestinal origin of the glands.

Source: Case