A 28-year-old woman had erosions on her oral mucosa and fingers for several months. A CT scan revealed an abdominal mass. Histopathology showed lichenoid dermatitis and immunofluorescence reticular deposition of IgG and C3 in the epidermis, leading to a diagnosis of paraneoplastic pemphigus (PNP). She underwent surgery with complete resection of the mass, postoperative pathology confirmed unicentric Castleman's disease of the hyaline vascular type. After surgery, she was treated with a reduced dose of oral glucocorticoids. After 2 years of follow-up, there was no recurrence of erosions of the oral cavity or the hand, and CT did not show the return of the mass. Complete resection is the first-line treatment for UCD with PNP, and early diagnosis is crucial for prognosis.