Light and electron microscopic studies of perineural invasion by esophageal carcinoma.

Light and electron microscopic findings on perineural invasion by human esophageal squamous cell carcinoma are reported. Perineural invasion was observed histologically in 30 of a total of 129 cases (23%) of esophageal squamous cell carcinoma and in 11 of the 24 cases (46%) in which tumors infiltrated other organs by passing through the esophageal adventitial layer. Electron microscopic observation showed that the perineurium of peripheral nerves was completely surrounded by carcinoma cells and that marked degeneration and loss of perineural cells occurred. Irregularly thickened basal laminae were detected in the perineurium. For nerves incompletely surrounded by carcinoma tissue, the free portion of the perineurium revealed degenerative findings similar to those for completely surrounded nerves. Cytoplasmic projections of the leading margin of the invading cancer tissue were located in the degenerated perineurium, contained many lysosomes, and were not always surrounded by basal laminae. These observations suggest that invading carcinoma tissue actively contributes to the degeneration of the perineural sheath and that the special pattern of carcinoma tissue surrounding the peripheral nerves results from infiltration along the degenerated sheath of the perineurium.