PT - JOURNAL ARTICLE AU - Aswathy Ashok Menon AU - Vikram Deshpande AU - David Suster TI - <em>MDM2</em> for the practicing pathologist: a primer AID - 10.1136/jcp-2022-208687 DP - 2023 May 01 TA - Journal of Clinical Pathology PG - 285--290 VI - 76 IP - 5 4099 - http://jcp.bmj.com/content/76/5/285.short 4100 - http://jcp.bmj.com/content/76/5/285.full SO - J Clin Pathol2023 May 01; 76 AB - The mouse double minute 2 (MDM2) gene is located on the long arm of chromosome 12 and is the primary negative regulator of p53. The MDM2 gene encodes an E3 ubiquitin–protein ligase that mediates the ubiquitination of p53, leading to its degradation. MDM2 enhances tumour formation by inactivating the p53 tumour suppressor protein. The MDM2 gene also has many p53-independent functions. Alterations of MDM2 may occur through various mechanisms and contribute to the pathogenesis of many human tumours and some non-neoplastic diseases. Detection of MDM2 amplification is used in the clinical practice setting to help diagnose multiple tumour types, including lipomatous neoplasms, low-grade osteosarcomas and intimal sarcoma, among others. It is generally a marker of adverse prognosis, and MDM2-targeted therapies are currently in clinical trials. This article provides a concise overview of the MDM2 gene and discusses practical diagnostic applications pertaining to human tumour biology.