I have scans of a histology slide of tissue of colorectal cancer and its surrounding tissue. This slide has been stained with the typical Hematoxylin & Eosin (HE) staining then unstained and stained again with two immunehistochemical markers, one for each B- and T-Lymphocytes. Those markers are CD3 for T-cells (which appears red) and CD20 for B-cells (which appears brown). The two scans were then aligned so that it is easy to identify a lymphocyte on the immunehistochemical stain (IHC stain) and find that exact cell in the HE stain.

After looking at these scans for some time I noticed, that there was a cell type that, to me, looks indistinguishable from a lymphocyte on the HE stain but clearly expresses neither CD3 nor CD20 when referencing the IHC stain. These cells are mostly found inside colon epithelium or cancer. Below are two images (one in the HE stain and one in the IHC stain) with two example cells marked with red arrows.

My question is what type of cell this is? Could it be some sort of precursor cell or sub-class of T- or B-cells, that expresses neither CD3 nor CD20? Is it even an immune cell at all?

HE stain

CD2/CD20 stain

  • 1
    $\begingroup$ There are immune cells, such as monocytes, macrophages, and dendritic cells, that don't express CD3 or CD20. I'm not enough of a histology expert to identify them on this slide, though. $\endgroup$
    – MattDMo
    Feb 28 at 18:49
  • 1
    $\begingroup$ Monocytes are, by definition, only present within blood vessels, macrophages have a large diameter with slightly uneven borders and a large amount of cytoplasm and dendritc cells aren't found inside epithelium to my knowledge. So I'd be very surprised if it was any of these cells. $\endgroup$ Mar 1 at 7:42

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