Morton's neuroma: an immunohistochemical study

Abstract Fifteen swellings of the interdigital nerve of 12 patients with Morton's metatarsalgia and 3 controls were studied by routine histology and immunohistochemical technique employing monoclonal antibodies against neurofilaments, human epithelial membrane antigen and a polyclonal antibody anti S-100 for the myelinic sheath. With the latter methods, individual nerve fasciculi were accurately identified in the context of the connective tissue mass of the ‘neuroma’. The basic aspect of the lesion showed by this study is the proliferation of connective cells affecting not only the perineurium and the endoneurium, but also individual nerve fasciculi. The latter were classified as compact or loose in relation to the fibrous proliferative process taking place inside fasciculi. Comparison of Morton's ‘neuroma’ and controls showed a prevalence of loosened fasciculi in the former. Fibroblastic proliferation and dissociation of the nerve fibres involved individual nerves in different degrees; no correlation was observed between pathological features and duration of symptoms. In more than two-thirds of cases in this series, Morton's metatarsalgia was associated with cavus or forefoot deformities.