Is there a first class relic of St. Pancras' pancreas?

Sadly, no. St. Pancras (c. 290-304, martyr, patron of teenagers) was executed by beheading under Emperor Diocletian. Beginning in 850 his head was at the Basilica of St. John Lateran but in 1966 was moved to the church of San Pancrazio in Rome.

A search did come up with Alain Tolhurst asking 'Can you tell the difference between St Pancras and a pancreas?' at London 24, but that's about pronunciation.