Lymphocytes are a heterogeneous group of cells with different origins, lifespans, and functions. They vary markedly in size. Some have a diameter of approximately 7µm, while others are as large as 18µm. The variations in size are mainly due to different amounts of cytoplasm. Therefore, the N:C ratio may range from 5:1 in some lymphocytes to 1:2 in others. The nucleus is about the size of a normal RBC. It is usually round or oval but may be slightly indented. The chromatin is very dense and clumped.
Small lymphocytes have a thin rim of clear, homogenous, moderate blue cytoplasm around the nucleus.
Lymphocytes do not contain specific granules. They occasionally have cytoplasmic azurophilic granules, also known as non-specific or primary granules.
