21st February 2025

A 32-year-old woman with a recent diagnosis of lymphoma presents to A&E with a 2 week history of worsening shortness of breath.

A 32-year-old woman with a recent diagnosis of lymphoma presents to A&E with a 2 week history of worsening shortness of breath. A chest X-ray in A&E shows a previously known mediastinal mass secondary to the lymphoma, as well as bilateral pleural effusions. A diagnostic pleural tap is carried out, which demonstrates milky white fluid. 

Which test on the pleural sample would be most helpful in confirming the cause of the effusions?

Select the SINGLE most appropriate option from the list below. Select ONE option only.