Serial sections of atrophic acne scars help in the interpretation of microscopic findings and the selection of good therapeutic modalities

Background Acne scar causes problems cosmetically and psychologically. Although microscopic examination of acne scars is a necessity for understanding and treatment of them, and it is not easy to find a paper reporting the microscopic characterization of acne scars. Objective The aim of this study was to examine the microscopic findings of acne scars and to select a good therapeutic modality based on the findings. Methods Thirty-one atrophic scars obtained from five patients for cosmesis and 18 serial sections were made from each atrophic scar. The sections were stained with H&E, Masson-trichrome or Verhoeff van Gieson stains. Immunohistochemistry was done with antibodies against transforming growth factor-β, metalloproteinase-1 (MMP-1), MMP-2, MMP-9 and MMP-13. The stained sections were examined under the microscope. Results The epidermis of the acne scar was characterized by keratin plugging in the hair follicle orifice (32%) and multi-channelled tracts (29%). The dermis of the acne scar had characteristics including a decrease in the dermal thickness and loss of pilosebaceous units. In addition, inflammatory cell infiltrates were seen in the dermis (77%), and insufficient dense collagen fibre deposition was found in the whole dermis (29%). Other findings such as calcium deposition and foreign body reaction were discovered. Conclusion We have found the characteristics of acne scar through the serial sections of several atrophic scars, and suggest that the treatment must reflect several considerations, including the understanding of histopathological findings and the use of combination therapy.