The importance of eosinophils and neutrophils infiltrating oesophageal squamous epithelium as markers for reflux, eosinophilic oesophagitis, and infection are well entrenched, although traditionally less attention has been paid to lymphocytes.

Small numbers of lymphocytes are normally seen in oesophageal epithelium including CD4 helper and CD8 positive cytotoxic lymphocytes.

However, isolated increases in lymphocytes in the oesophageal epithelium, outside the context of entities such as lichen planus and graft versus host disease, have been less well recognised until recently.