The difference between lymphoma and chyle
Remember that just because you see lymphocytes in an effusion doesn’t automatically mean it’s lymphoma.
The case on the left here is lymphoma from a pleural effusion. We know that because the cells are intermediate to large in size.
The case on the right is chyle. Chylous effusions are predominated by small lymphocytes (also often have vacuolated macrophages +/- neutrophils in the mix).
Size matters when it comes to interpreting lymphoid populations!