The following is a summary of “Comparative Immunohistochemical Analysis of Macrophage Phenotypes in Cutaneous Sarcoid Granuloma, Suture Granuloma, and Lipogranuloma,” published in the June 2023 issue of Dermatopathology by Nakamura et al.
Granulomas comprise a heterogeneous population of resident and recruited macrophages based on the type of lesion, the extent of injury, and the local tissue environment (e.g., the site involved and the interaction with infiltrating lymphocytes). Although macrophage phenotypes in various forms of granulomas have been described previously, the varying experimental conditions between studies prevent a comparative and exhaustive understanding of granulomas.
Under strict conditions, this study was conducted to compare the expression of M1 and M2 phenotype markers in macrophages comprising various granulomas, including epithelioid lesions. About 11 lesions of cutaneous sarcoidosis, 10 lesions of suture granuloma, and 12 lesions of subcutaneous lipogranuloma were stained immunohistochemically for CD11c, CD206, CD163, and CD10. Each form of granuloma’s macrophage expression of these markers was measured and statistically analyzed. In most cases, granuloma macrophages were immunoreactive for CD11c and CD206.
However, in 5 cases of lymphogranuloma, numerous CD206-negative cells were observed. CD163 and CD10 were diffusely expressed in suture granuloma and lymphogranuloma macrophages but not in the epithelioid cells of cutaneous sarcoidosis. In 7 cutaneous sarcoidosis lesions, “interstitial” macrophages surrounding epithelioid granulomas demonstrated moderate to CD163 tangible expression. The expression of CD163 and CD10 significantly differs between cutaneous sarcoidosis and suture granuloma/lymphogranuloma; CD163 and CD10 are downregulated in cutaneous sarcoidosis after the epithelioid transformation of macrophages.