**3. Histology**

A small amount of intraepithelial lymphocytes is normally present in the esophagus [4, 5]. A majority of these lymphocytes are CD8 T cells, whereas CD4 are a minority and usually present in the lamina propria. An increase in CD8 T cells is seen in peptic and eosinophilic esophagitis. In addition, this lymphocytosis is generally accompanied by eosinophils and/or neutrophils [5–8].

Compared to other esophageal pathologies, lymphocytic esophagitis is characterized by an isolated lymphocytosis. The main histologic findings are a dense peripapillary intraepithelial lymphocytic infiltrate, an intercellular edema known as spongiosis, as well as the absence or rarity of granulocytes (**Figure 1**) [1]. The intraepithelial lymphocytes express CD3, CD4, and CD8, as shown by immunohistochemistry [1, 9, 11].

Unfortunately, because the histologic criteria are not yet standardized, it can sometimes lead to misdiagnosis. For instance, the presence of rare intraepithelial granulocytes is accepted in lymphocytic esophagitis [1, 2, 10, 11]. However, granulocytes can be found in various esophageal diseases, making diagnosis more difficult [11]. The acceptable number of granulocytes still needs to be better defined.

**Figure 1.** Lymphocytic esophagitic (H&E stain, original magnification ×40). Dense peripapillary lymphocytic infiltrate with spongiosis (arrow). Absence of neutrophils and eosinophils.

Because the lymphocytosis is patchy and uneven, we suggest not to establish a minimum number of intraepithelial lymphocytes [2]. In fact, the various studies about this entity have all used different cutoff, ranging between 10 and 50 lymphocytes per high-power field (HPF) [2, 3, 12, 13].

Furthermore, lymphocytic esophagitis affects the whole esophagus, but predominantly the distal esophagus. Thus, multiple biopsies are necessary to avoid a false negative because the lymphocyte infiltrates are not distributed evenly throughout the entire esophagus [12].

The mucosal involvement is considered mild if the intraepithelial lymphocytosis is only peripapillary and is severe if there is also an interperipapillary lymphocyte infiltration [12].
