Granulomas on FNA: recognizing and ruling out malignancy
May 2025—Granulomas are organized clusters of immune cells that form as part of the body’s chronic inflammatory response, typically triggered by persistent antigens, chronic infections, or immune dysregulation. They develop when macrophages are activated, transforming into epithelioid histiocytes and multinucleated giant cells (MGC) in response to ongoing immune stimulation. Granulomas are usually surrounded by T lymphocytes, fibroblasts, and extracellular matrix components. While granulomas are most often associated with infections or autoimmune conditions like sarcoidosis, they can arise in a variety of other processes, including malignancy.