The invention relates to a method for detecting a foreign cell in a tissue of the upper intestinal tract, sold method comprising: (a) providing a sample of cells from the epithelium layer of the tissue of interest； (b) preparing the cells into a cohesive cluster； (c) staining cells from the cohesive cluster using haematoxylin and eosin (H&E) stain； (d) observing the stained cells； and (e) inferring the presence or absence of foreign cell(s) from the observations of Id), The invention also relates to a method for aiding the diagnosis of an inflammatory condition of the upper intestinal tract in a subject, said method comprising detecting a foreign cell as described above, wherein detection of foreign cell(s) in step (e) infers that the subject has an inflammatory condition of the upper intestinal tract.
