IntroductionCondyloma acuminatum are caused by human papillomavirus. Giant condyloma acuminatum is a locally invasive, destructive, and large sized mass. Risk factors for the development of giant condyloma acuminatum include an immunodeficient state, such as human immunodeficiency virus infection, post-organ transplantation, or post-allogeneic bone marrow transplantation. However, reports of giant condyloma after bone marrow transplantation are extremely rare (0.3 to 1.3%). The standard treatment for giant condyloma acuminatum is recommended as wide surgical resection due to its high rate of success and low rate of recurrence.Case presentationA 31-year-old Korean man presented to our hospital with anal discomfort for more than one month due to a protruding mass. He had a history of BCR-ABL-positive acute lymphoblastic leukemia and had undergone an allogenic stem cell transplantation. Gross findings revealed a large perianal cauliflower-like mass over 7cm in size with invasion of the anal orifice. He was diagnosed with giant anal condyloma occurring after an allogeneic bone marrow transplantation. However, we achieved successful treatment using a combination of topical podophyllin and cryotherapy and transanal surgical excision, followed by bleomycin irrigation.ConclusionsWe report an extremely rare case of giant condyloma acuminatum of anus due to human papillomavirus type six in a patient with acute lymphoblastic leukemia following an allogeneic bone marrow transplantation. The tumor was successfully treated with a combination of topical podophyllin and cryotherapy and transanal surgical excision, followed by bleomycin irrigation.