Differentiating primary Paget's disease from secondary Paget's disease, which is also known as Pagetoid growth of other cancers, in the perianal region is difficult. Given that the treatment strategies of both disease are significantly different, diagnosis of such conditions should be performed with caution. We report a case of secondary Paget's disease. A 76-year-old man previously visited a hospital because of erythematous plaque around the anus. It was diagnosed as extramammary Paget's disease based on skin biopsy results; consequently, perianal skin resection was performed. Pathological examination of the resected specimen indicated Pagetoid growth of mucinous carcinoma, and it was positive for stump. Consequently, laparoscopic abdominoperineal resection was performed. Finally, the plaque was diagnosed as anal canal adenocarcinoma with Pagetoid growth, and all the previous results were deemed as initial diagnosis.
Conclusion: Discriminating between primary and secondary Paget's disease, even with immunohistological techniques, is difficult. Novel methodology that might facilitatemoreaccuratediagnosis preoperatively for erythematous plaquearound theanus and morecurativethe rapeutic strategy are needed.