mitotic index

Full Definition

Mitotic index is a histopathological parameter that quantifies the number of cells undergoing division (mitosis) per unit area or number of cancer cells examined. In breast cancer, it forms one component of the Nottingham histologic grade along with nuclear grade and tubule formation. The mitotic count is typically assessed per 10 high-power fields and contributes to determining tumor grade (1, 2, or 3). Higher mitotic indices indicate more rapidly dividing tumors and are associated with more aggressive behavior and poorer prognosis.

Usage

Usage note: Often expressed as number per 10 high-power fields (HPF) or per square millimeter.

In Context

• "The elevated mitotic index contributed to the grade 3 tumor classification." — histopathology report
• "Mitotic index assessment requires careful examination of mitotic figures in tumor areas." — pathology methodology