Tendency of fluorouracil to conceal deep foci of invasive basal cell carcinoma.

Topical fluorouracil treatment of invasive basal cell carcinomas (BCC) is not recommended because it often produces the appearance of control with superficial inhibition of the tumor as the deeper extensions continue to grow, which results in a needless delay in obtaining effective treatment. These conclusions are based on data obtained during the microscopically controlled excision of 103 invasive BCCs of the face that had recurred after topical fluorouracil treatment.