Vulvar lichen sclerosus progressing to squamous cell carcinoma due to the poor compliance for the follow-up after ALA-PDT

5-Aminolevulinic acid photodynamic therapy (ALA-PDT) is an effective modality for vulvar lichen sclerosus (VLS) and squamous cell carcinoma (SCC) in situ. Here we first describe a case of VLS that relapsed after ALA-PDT without follow-up and progressed to SCC eventually. The first two courses of ALA-PDT (total of 21 sessions) were effective for VLS. The third course of ALA-PDT (2 sessions) was changed to the surgery because of SCC was diagnosised. In our case, we emphasis that maintain regular follow-up to treat the recurrent lesions to prevent the development of SCC.