Differential Diagnosis of Tuberculoid Leprosy from Sarcoidosis by S-100 and Computer-assisted Image Analysis

Abstract

Background: Histologic evidence of destruction of a cutaneous nerve by granulomatous inflammation is a feature of tuberculoid leprosy. However, identifying remnants of the nerve in the granuloma may be difficult in some instances because of morphologic similarities with granulomatous dermatoses, such as sarcoidosis, lupus vulgaris, tertiary syphilis, etc. Object: The purpose of this study was to investigate the expressions of S-100 and EMA and to estimate area, thickness and density of nerves for differentiation tuberculoid leprosy from sarcoidosis. Methods: Paraffin embedded tissues from patients of 11 tuberculoid leprosy, and 4 sarcoidosis were investigated for the expression of S-100, EMA and for the measurement of area, thickness, density of nerves by image analysis. Results: 1. S-100 staining in tuberculoid leprosy demonstrated fragmented, infiltrated, swollen nerves or the absence of dermal nerves(45.5%). 2. All of the detectable nerves were identified within granulomas from tuberculoid leprosy, but nerves from sarcoidosis were widely distributed over inside(33.3%) or outside of the granulomas, perivascular, and periappendageal areas. 3. There was no expression of EMA in skin lesions from leprosy, sarcoidosis, even in the site showing perineural thickening in S-100 stain. 4. The cross-section area and the thickness of nerves were decreased in order of tuberculoid leprosy, sarcoidosis, and normal control group(plt;0.05). 5. The density of nerves was decreased in order of normal control group tuberculoid leprosy, and sarcoidosis with statistical significance between tuberculoid leprosy and sarcoidosis. Conclusion: It is possible to differentiate tuberculoid leprosy from sarcoidosis by the observation of the morphologic changes with S-100 protein stain and the measurement of the cross-section area, thickness and density with image analysis.