S-100 protein and immunoperoxidase technique as an aid in the histopathologic diagnosis of leprosy.

The histopathologic diagnosis of leprosy in the tuberculoid type (TL) and in the indeterminate group (IL) may be difficult and frequently unfeasible. The detection of the impairment of cutaneous nerve branches by the inflammatory reaction may permit the diagnosis of TL over other skin granulomas. In an attempt to overcome these diagnostic difficulties in the lesions with no bacilli and without obvious damage to nerve branches, we utilized the immunoperoxidase technique with S-100 protein as the nerve marker. Two groups were selected: Patients (group 1) with TL confirmed by the presence of bacilli, and patients (group 2) with a clinical diagnosis of TL not confirmed by histopathology. The slides treated by S-100 in group 2 showed that 8 cases (9 total) were confirmed to have TL on the basis of the nerve alteration observed by the immunoperoxidase technique. These data obtained in the present studies show that use of the immunoperoxidase technique for the detection of S-100 protein to visualize peripheral nerves represents an efficient auxiliary aid in the diagnosis of leprosy.