Similar to peripheral blood, lymphocytes in fluids come in all sizes. A larger lymphocyte is not necessarily an abnormal or atypical lymphocyte, however.
In the image shown here there is an atypical lymphocyte (blue arrow) adjacent to the monocyte at the top of the smear. The atypical lymphocyte is almost as big as the monocyte; however, the nucleus is more regular. The amount of cytoplasm is similar between the two cells, but the atypical lymphocyte has a deeper blue shading at the edge of the cytoplasm.
Though there are nucleoli present in this atypical lymphocyte, it does not necessarily mean that this is a malignant cell. Cytocentrifugation can expose nucleoli in cells that would not normally appear in the cells on a peripheral blood smear. The balanced amount of cytoplasm in comparison to the nucleus and the overall size of the cell are consistent with the range of variation found with atypical lymphocytes.
In this smear, there is also an atypical (plasmacytoid) lymph in the lower left of the cluster (green arrow) and a basophil in the lower right (orange arrow).