The histopathological approach to granulomatous skin lesions

Abstract

Granulomatous inflammation of skin and subcutaneous tissue are common in India. An identical histological picture is produced by several causes. Present study aims at classifying infectious granulomas based on histomorphology and special staining and developing a proper approach for making a specific etiological diagnosis. To classify the granulomatous dermatitis and a simple diagnostic histological approach has been worked out based on morphology of granuloma, presence of caseous necrosis, palisading necrosis, location of the granuloma and use of special stains. A prospective study of skin biopsies with granulomatous inflammation over a period of 2 years is done. Histologically lesions were divided into six subtypes:-Tuberculoid, foreign body type, histoid, necrobiotic, suppurative and sarcoidal type. On basis of morphological features and special staining each type was further subclassified and a specific diagnosis was given. Among 580 skin biopsies, 175 cases (30.17%) were of granulomatous skin lesions. On histopathological typing Tuberculoid type of granuloma was the most common type (62/175 cases, 35.43%) of which leprosy (40/62 cases, 64.52%) was the commonest etiology identified. Infections form an important etiology of granulomatous skin inflammation (120/175 cases, 68.57%) of which leprosy (82/120 cases, 68.33%) is the leading etiology in our study. Adequate clinical work-up in combination with pathological resources help in correctly approaching a granulomatous skin lesion and reaching a specific etiologic diagnosis.