In pathology, perineural invasion, abbreviated PNI, refers to the invasion of cancer to the space surrounding a nerve. It is common in head and neck cancer, prostate cancer and colorectal cancer.
Micrograph showing a prostate cancer (conventional adenocarcinoma) with perineural invasion. H&E stain.
Micrograph demonstrating perineural invasion. HPS stain.
A nerve is an enclosed, cable-like bundle of nerve fibers in the peripheral nervous system.
Cross-section of a nerve
Micrograph demonstrating perineural invasion of prostate cancer. H&E stain.