Hodgkin’s disease, is a type of lymphoma, and is also referred to as Hodgkin’s lymphoma. The disease will spread from one lymph node group to another in an organized manner. During the advanced disease stages, systemic symptoms will usually develop. A common histopathologic finding is multinucleated Reed–Sternberg cells, which are the neoplastic cells of Hodgkin’s lymphoma.
CD15 is useful for the differential diagnosis of Hodgkin disease vs. non-Hodgkin lymphomas and for classification of leukemia. The ratio of CD15 positive cells is an indicator for the progression and aggression of the disease. In some neoplastic diseases like Hodgkin disease, myeloid leukemia and gliomas, CD15 expression is inversely correlated to dedifferentiation and progression.
In CD15 positive cells the antigen expression may be membranous, diffuse cytoplasmic or related to the Golgi zone and is expressed on most terminally differentiated myeloid cells (granulocytes, monocytes/histiocytes and Langerhans cells).
Here, CD15 is heavily expressed in the cytoplasm of the neutrophil granulocytes, making it difficult to see the nucleus of the cells when the chromogen is filling the cytoplasm. CD15 is more moderately expressed in the neoplastic Hodgkin and Reed-Sternberg cells. The cell and nucleus diameter of these cells are also often far larger than the diameter of the neutrophil granulocytes. Therefore, the Hodgkin and Reed-Sternberg cells will appear as cells with a (negatively stained) large nucleus or multi nuclei surrounded by brown cytoplasm, where the staining is less dense than for the neutrophil granulocytes. The cell area of a neoplastic cell will usually be at least 400 µm.
Smaller, single nucleus cells, with intense staining (or where the nucleus is not visible due to the density of the chromogen) will most likely be neutrophil granulocytes.
The purpose of the APP is to locate and segment the number and area of the neoplastic cells, as well as determine the positive ratio compared to the total analyzed area.