Perianal Paget's Disease From Underlying Anal Adenocarcinoma: A Case Study.

Perianal Paget's disease (PPD) is a rare intraepithelial adenocarcinoma with epidermatotropic features, which often presents with common dermatological conditions such as eczema, hemorrhoids, and sensations of itching and burning. Due to these nonspecific symptoms and limited data related to this rare disease, its diagnosis is often delayed. However, as this disease is often secondary to an underlying malignancy, its early diagnosis may prevent fatal outcomes.    This case report discusses a 76-year-old female patient with a family history of colon cancer who presented with anal pain, bleeding hemorrhoids, and a perianal mass. The initial lesion was removed using transanal excision surgery. Several months later, a PET/CT scan showed hyperintense lymph nodes in the right external iliac vessels; upon biopsy, metastatic anal adenocarcinoma was diagnosed. The patient underwent subsequent systemic chemotherapy and chemoradiation.  This case emphasizes the diagnostic pitfalls in the setting of coexisting pelvic pathology and the importance of early detection, recognition of variance in immunohistochemical markers, and timely interventions in PPD for the most efficacious treatment. It also highlights the need to determine the source of PPD and to increase physician awareness of secondary PPD arising from anal adenocarcinoma.