A topical ointment formulation containing a synthetic form of hypericin, an anthraquinone derivative that is naturally found in the yellow flower of Hypericum perforatum (St. John's wort), with potential antineoplastic and photosensitizing activities. Upon topical administration of the ointment to the tumor site, hypericin becomes activated through the application of visible fluorescent light. During photoactivation, hypericin generates singlet oxygen, which induces DNA damage, necrosis and apoptosis, thereby inhibiting tumor cell growth. The use of visible light for activation avoids the risk of developing secondary malignancies, which are frequently associated with other photodynamic therapies that are dependent on ultraviolet A exposure.