Perineural spread of cancer

Perineural invasion (PNI) refers to a rare type of contiguous spread of neoplastic cells from their primary site along the potential space between or beneath the layers of perineurium. This entity is best described in cancers of the head and neck but is also well described in other solid tumors. Exact pathogenesis remains unclear, but proximity of the primary tumor to major nerves and plexus and the tumor cell’s ability to infiltrate and proliferate within the perineural space, as well as directed molecular interactions between the tumor and its microenvironment, are thought to play an important role. Clinical presentation varies depending on the nerves involved. Developing a broad differential to include direct compression of nerves by tumors, delayed effects of prior radiation therapy, infections, and paraneoplastic syndromes as well as work up for other common causes of neuropathies is encouraged. Contrast enhanced magnetic resonance imaging is the imaging modality of choice but a biopsy is frequently required for conformation of diagnosis. Accurate detection may help predict prognosis and guide therapy. We recommend a multidisciplinary approach in selecting the curative and palliative treatment options.