Nonneoplastic

Nonneoplastic is a term used in pathology and medicine to describe lesions, tissue changes, or processes that do not arise from clonal proliferation of neoplastic cells. In practice, nonneoplastic conditions include inflammatory, infectious, degenerative, metabolic, vascular, and reparative processes, as well as congenital malformations and other benign tissue alterations that are not true neoplasms. By contrast, neoplasms are growths driven by genetic alterations that lead to autonomous cell proliferation.

Common nonneoplastic conditions include inflammatory and infectious processes, fibrosis and scar formation after injury, granulomatous inflammation, abscesses, simple cysts, edema, and tissue necrosis with subsequent repair. Reactive or compensatory hyperplasia may be nonneoplastic when it represents a non-autonomous tissue response rather than independent neoplastic growth. Some developmental malformations, such as hamartomas, are considered nonneoplastic in nature rather than true tumors, reflecting disorganized but native tissue elements.

Diagnosis and clinical relevance: distinguishing nonneoplastic from neoplastic processes is important because management, prognosis, and surveillance differ. Imaging and clinical presentation can be insufficient to differentiate them; histopathology, immunohistochemistry, and, when appropriate, molecular testing help determine clonality and lineage, guiding treatment toward conservative management for many nonneoplastic conditions and targeted therapy for neoplasms.

Limitations and terminology: the boundary between nonneoplastic and neoplastic can be nuanced, and some lesions may be difficult to classify. The term is used to emphasize absence of neoplastic clonal proliferation rather than to imply benign behavior in all cases.