In addition to the 5FU injections, a subset of study participants will also have their lesions treated concomitantly with a topical application of 5% imiquimod, another well-characterized chemotherapeutic agent with some demonstrated efficacy in treating cutaneous squamous cell carcinomas. The investigators hope that the concomitant use of topical 5% imiquimod will work synergistically with intralesional 5FU. No study published to date has been found on the concomitant use of intralesional 5FU and topical imiquimod.