NK T-cell lymphoma is a highly aggressive cancer of a specific type of immune cell called lymphoid cells, and is associated with the Epstein Barr virus (glandular fever). In later stages of the disease, the lymphoma can spread to the lymph nodes, as in this case.

The stain 'Romanowsky Giemsa' May Grünwald Giemsa (MGG) can be used for diagnosis. It stains DNA purple and RNAblue. Here, the nucleus, or 'brain' of the cells shows as purple, with the RNA seen in regions of the cell called the nucleolus. The image shows red blood cells (orange/pink cells), several benign (non-cancerous) small lymphocytes (white blood cells) (dark purple cells) and malignant lymphoid cells with immature chromatin (DNA). The lymphoid cells are the larger cells seen here, presenting granules outside of the nucleus (in the cytoplasm), evident in this example as purple dots. The granules are usually referred to as "azurophilic" referring to their affinity to the myriad azure dyes that form through oxidation of the chemical methylene blue and constitute the major component of Giemsa stain. Horizontal image width 135 micrometres