Castleman disease (CD) is a rare lymphoproliferative disorder that can present with nonspecific symptoms, making diagnosis challenging, particularly in elderly patients. This case report describes a 93-year-old woman who presented with intermittent abdominal pain, which was unresponsive to standard treatments and showed no systemic signs of infection or malignancy. Initial imaging revealed scattered lymphadenopathy, raising concern for a lymphoproliferative disorder. A laparoscopic lymph node biopsy was performed, leading to a diagnosis of unicentric CD (UCD). The patient was treated with corticosteroids, which resulted in a marked improvement in her symptoms, including the complete resolution of her abdominal pain. This case emphasizes the importance of considering CD in the differential diagnosis of unexplained abdominal pain in elderly patients, as early diagnosis and treatment can prevent complications and significantly improve outcomes. The successful use of corticosteroids in this patient highlights a nonsurgical treatment option for UCD in cases where surgical excision is not feasible.