Castleman's disease is a very rare disease that causes many problems both in diagnosis and therapy. It is often associated with other diseases and can develop in any part of the body. Castleman's disease can be classified as uni-centric or multicentric based on clinical and radiological findings, as hyaline-vascular or plasma-cell based on the histological aspect, and as HIV-related or non-HIV-related, based on the HIV status of the patient. An inflammatory fibroid polyp is a very rare benign lesion that can develop anywhere in the gastrointestinal tract. Such polyps are most commonly found in the gastric antrum and usually occur in 50- to 60-year-old people. The authors report the unusual finding of mesenteric Castleman's disease and an inflammatory fibroid polyp of the stomach in a 41-year-old woman.