A case of Crohn's-disease-associated anal canal cancer with p53-positive dysplasia: suggesting insights to stepwise carcinogenesis.

Crohn's-disease-associated colorectal cancer, where chronic inflammation increases the risk of cancer development, is less common than other types of colorectal cancer. Pathological analyses of Crohn's-disease-associated colorectal cancer are limited. Herein, we present a case of Crohn's disease-associated colorectal cancer, suggesting stepwise carcinogenesis from the chronic inflammatory mucosa. A man in his 40s had a 28-year history of Crohn's disease with perianal involvement for over 20 years. He visited our hospital due to worsening anal pain and fecal incontinence. Following clinical evaluation, he was diagnosed with anal canal cancer and subsequently underwent surgery. Histopathological examination revealed cancer originating from the chronically inflamed mucosa, suggesting p53-positive dysplasia, well-differentiated adenocarcinoma, and subsequently, mucinous adenocarcinoma. The final diagnosis was Crohn's-disease-associated anal canal cancer. Despite postoperative adjuvant chemotherapy, he exhibited pelvic recurrence and distant metastasis 20 months postoperatively. A comprehensive multidisciplinary treatment intervention was implemented; however, he eventually succumbed to cancer progression 3 years after surgery. This case suggests inflammation-associated stepwise carcinogenesis, demonstrating tumor heterogeneity and providing insights into dysplasia. Despite improved understanding from recent registry studies, the diagnosis and treatment of CD-CRC remain challenging in clinical practice, as seen in this case.