Perianal Paget's disease complicated with lung adenocarcinoma and anal canal carcinoma: A case report and literature review.

Perianal Paget's disease (PPD) is a rare malignant cutaneous tumor. This paper reported a case of PPD complicated by lung adenocarcinoma and anal canal cancer. The patient, a 76-year-old female, had been experiencing recurrent lower abdominal pain and perianal pruritus for the past 5 years. Upon physical examination, a cauliflower-like neoplasm in size of 5 cm×6 cm was observed on the right perianal skin, with local skin ulceration and a small amount of fluid discharge. The left perianal skin was also involved. In thoracoknee position, a hard mass was palpable in the rectal submucosa at 5-6 points 2 cm from the anal verge. Chest CT revealed multiple lesions in both lungs, indication of metastatic tumors. Further evaluation with fluorodeoxyglucose positron emission tomography and computed tomography (FDG-PET/CT) indicated multiple hypermetabolic nodules in the lungs, hypermetabolic lymph nodes throughout the body, early FDG uptake in a small patch of skin on the left hip, and increased FDG uptake in the anorectal region. Histopathological examination confirmed the diagnosis of lung adenocarcinoma. This resulted in the patient being diagnosed with PPD, lung adenocarcinoma, anal canal cancer, and systemic multiple lymph node metastasis. The combination of PPD with gastrointestinal tumors and other metachronous malignant tumors is highly prevalent. Colonoscopy, FDG-PET/CT, histopathology, and immunohistochemistry play crucial roles in early identification of local lymph node and distant involvement, facilitating the evaluation of potential malignant tumors and differential diagnosis. Treating methods for PPD are currently diverse, including postoperative combined or single chemotherapy, radiotherapy, targeted therapy, and photodynamic therapy. As trerapeutical options continue to develop, the extent and efficacy of surgery need to be reassessed.