Perineural spread by squamous carcinomas of the head and neck: a morphological study using antiaxonal and antimyelin monoclonal antibodies.

Perineural spread has been demonstrated histologically in 65/180 (36%) major surgical resections for squamous carcinomas of the head and neck; the incidence in a smaller necropsy series was 18/20 (90%). Perineural infiltration was observed most commonly in the vicinity of carcinomas arising in the buccal cavity (31/63, 50%) and, at all sites, it was most commonly encountered near tumours less than or equal to 2.5 cm in diameter. Perineural spread near cervical node metastases was, by contrast, uncommon in the surgical series. Tumour within perineural spaces tends to be concentrated at the margin of the nerve and shows only limited extension inwards, but cells may track upwards and downwards within the spaces. Distant spread for greater than 2 cm is unusual, and interval sampling of involved nerves in necropsy material indicates that most perineural tumour cells are confined to the distal 1 cm of the affected nerve. Infiltrated nerves regularly show varying degrees of myelin and axonal degeneration, probably anoxic in origin, and segmental infarction of nerve trunks was observed in three patients. Fine changes in axons and myelin have been regularly demonstrated with two monoclonal antibodies, and the use of these new reagents is described.