The trephine shows the typical “fried egg cells” seen in hairy cell leukaemia.  The cells appear widely spaced due to abundant cytoplasm, with broad projections.

  This is typical hairy cell which may be found on the peripheral blood film – although in this case we were unable to see this on the peripheral blood smear.

How would you manage this patient now that you have confirmed the diagnosis?

BRAF mutation has previously been mentioned during this case.  Can this be found in any other diseases?

What if the BRAF mutation was negative?