ALA-PDT combined with CO₂ laser in the treatment of malignant hidroacanthoma simplex: A case report

Hidroacanthoma simplex (HS) is a rare skin appendage tumor that typically appears on the trunk and lower limbs in the elderly. Although HS is a predominantly benign condition, the presence of cellular atypia and dermal infiltration on histological examination indicates malignant HS (MHS). 5-aminolaevulinic acid photodynamic therapy (ALA-PDT) uses a photosensitizer and corresponding light source to cause irreversible damage or death of target cells through a photochemical reaction. Here, we reported the successful treatment of a MHS patient with ALA-PDT using plum-blossom needle pretreatment combined with CO₂ laser. After five courses of ALA-PDT, the lesions were completely resolved, and the autonomic activity and smooth surface of the left ring finger were restored. This suggests that ALA-PDT is an effective, minimally invasive and safe treatment modality for MHS.