Myofibroblasts, B Cells, and Mast Cells in Different Types of Long-Standing Acne Scars

Acne scars are classified into various types based on their appearances, ranging from hypertrophic to atrophic. Abnormal wound healing processes play an important role in the pathogenesis of scars; however, the exact mechanisms involved in various scar appearances have still not been elucidated. In this study, we used immunofluorescence and immunohistochemistry techniques to detect the presence of myofibroblasts, B cells, and mast cells in each type of acne scar persisting longer than 6 months. We found the highest density of myofibroblasts in hypertrophic acne scars, while in the other atrophic scars, we could not identify any myofibroblast-rich areas in our specimens. B-cell infiltration was mild and found in only 23% (4/17) of all acne scar specimens. Interestingly, mast cells were identified in all specimens, ranging from minimal to high density, and a high number of mast cells in acne scars were associated with obesity. In conclusion, myofibroblasts are abundant only in hypertrophic acne scars, and mast cells, but not B cells, might play an important role in the pathogenesis of long-standing acne scars.