[Rapidly growing squamous cell carcinoma after ingenol mebutate treatment].

Introduction: Ingenol mebutate is an actinic keratosis treatment, which has a dual action mechanism. It allows a rapid cellular death and a severe inflammation.

Observation: We report the case of a 75 years old patient with a rapidly growing tumor 5 weeks after application of ingenol mebutate on typical actinic keratosis. Histological analysis after surgical excision showed an invasive squamous cell carcinoma (SCC); with aggressiveness signs: perineural infiltration and vascular permeation.

Discussion: Ingenol mebutate's common side effects are benign and regressive within 2 to 4 weeks. There are erythema, edema, crusts, and ulcerations/erosions. Squamous cell carcinoma development was rarely reported. We have tried to collect other cases in the literature and in pharmacovigilance centres: three similar cases were recently published in the literature, 21 cases were notified to the European Medicines Agency and we asked French pharmacovigilance centres and found 5 cases of SCC after ingenol mebutate application. The role of the molecule in SCC development is currently unknown. Induced inflammation could take part in the development of these tumors. We compare this case with other situations of inflammation, such skin graft donor site or surgical incision, complicated of rapidly growing SCC. Our case, literature's and pharmacovigilance's cases encourage us to follow ingenol mebutate's side effects. Careful follow-up and registration of such cases are important to gain further insight on this topic.