The cell depicted with the arrow in this image is an atypical (reactive) lymphocyte. These cells are common found in certain viral infections, especially infectious mononucleosis. Notice the larger size and abundant cytoplasm present in this lymphocyte. There is also apparent vacuoliation which is a key feature of atypical lymphocytes. The chromatin pattern of this cell as well as the overall shape, color and size rules out the monocyte, macrophage, and mesothelial cell choices.

A patient with an infectious mononucleosis infection presents in the emergency room. Physicians order a spinal tap which is immediately sent to the laboratory for review. Please identify the cell in the image below from this patient's cerebrospinal fluid sample.