CD163-positive macrophage infiltration predicts systemic involvement in sarcoidosis

Background Sarcoidosis is a chronic and systemic inflammatory disease, in which patients present with noncaseating epithelioid granulomas. Cutaneous lesions of sarcoidosis develop in 9% to 35% of all sarcoidosis patients and comprise various clinical subtypes. It usually affects multiple organs and has a variable clinical course; this is called systemic sarcoidosis (SS). However, occasionally, it only affects the skin and is then called cutaneous sarcoidosis (CS). Recent observations suggest that serum levels of soluble CD163 correlate with immune cell activity in sarcoidosis patients; however, the contribution of M1 and M2 macrophages toward disease progression remains unclear. Methods We evaluated macrophage phenotypes histopathologically using skin biopsy samples obtained from patients with CS (n = 8) and SS (n = 31) and performed immunostaining with CD68, iNOS (M1 macrophages), PD-L1, and CD163 (M2 macrophages). Results The density of CD163-positive cells in the SS group was significantly higher than that in the CS group. There was no significant correlation between the CD163 (+) cell density and serum angiotensin-converting enzyme level, serum calcium, or tuberculin reaction. Conclusions Immunostaining for CD163 may be a novel and useful marker to predict systemic involvement in patients with cutaneous lesions of epithelioid granulomas.