Atypia refers to the presence of abnormal cells or cellular changes in a tissue sample. There are several synonyms for this medical term, including dysplasia, cellular atypism, and abnormal cytology. Dysplasia refers specifically to abnormal tissue growth, while cellular atypism and abnormal cytology describe the abnormal appearance of cells. Other related terms include neoplasia, which refers to the formation of a new growth or tumor, and metaplasia, which refers to the transformation of one cell type into another. These terms are often used in the context of cancer diagnosis and treatment, as the identification and classification of abnormal cells is critical in determining the course of treatment.