Anal canal squamous-cell carcinoma in situ, clearly demonstrated by indigo carmine dye spraying: report of a case.

To our knowledge, there has been no report of the use of indigo carmine dye spraying for the diagnosis of intraepithelial neoplasia. An asymptomatic 58-year-old female was referred to our hospital with a diagnosis of squamous-cell carcinoma in the anal canal. After indigo carmine dye spraying the margin and surface appearance of the lesion could be clearly defined. The lesion was completely removed by transanal resection. Final histologic diagnosis was squamous-cell carcinoma in situ with koilocytosis. Our case suggests that indigo carmine could be useful for the diagnosis of intraepithelia neoplasia.