Hanger Mandrel : That portion of a casing or tubing hanger which is attached by a threaded connection to the tubular string and forms the upper end of that tubular string. (Spec 6A).
The Mudblogger (Oilfield, Energy and Related Photographs), Oil Field Glossary, TX, USA 2014. http://mudblogger.com/oilfield-glossary/, (Oil - Amer) {777}