Cell mediated immunity was primarily thought to mediate the pathogenesis of sarcoidosis. However, the presence of immunoglobulins, immune complexes, and complement suggests that processes of humoral immunity may contribute to immunopathology in sarcoid lesions.The pattern of sarcoidal granuloma includes a variety of systemic and cutaneous diseases, including sarcoidosis, foreign-body reaction, metastatic crohn’s disease and papular rosacea. Pathologically, sarcoidosis may be hardly separated from lupus vulgaris especially if lymphocytes are abundant than usual. Also, tuberculoid leprosy may be difficult to be distinguished from sarcoidosis. However, immunoglobulin M was found to be deposited in sarcoidal lesions only. So, it can be used as both diagnostic and differentiating factor between them.