Pericellular lacunae in effusions.

Pericellular lacunae are reported to be characteristic of adenocarcinoma cell clusters in cell block preparations of serous effusions. We examined the incidence of lacunae in cell blocks from 24 benign and 31 malignant effusions. The cases were classified as follows: group A with no pericellular lacunae, group B with < 50% of cell clusters in lacunae, and group C with > 50% of cell clusters in lacunae. Of the malignant effusions, 5% were in group A, 67% were in group B and 29% were in group C. Of the benign effusions, 50% were in group A, 50% were in group B, and 0% were in group C. The pericellular lacuna by itself is not a reliable diagnostic criterion. It could assist, however, in the overall evidence when evaluating a case, particularly if either there are no lacunae seen or the majority of cells are in lacunae. Furthermore, since lacunae are easily visible at low magnification, their recognition may help in screening cell blocks, using their presence to locate cell groups worthy of special attention.