Low power view of lymph node. Notice the wide, curving, intersecting collagen bands separating the node into nodules.
At higher power, you can see that a nodule consists of a relatively small number of loosely clustered lacunar cells which are neoplastic. The lacunar cell is the variant of Reed-Sternberg cell that is found in NSHL. Its nucleus is smaller and finer than the RS cell, and the cytoplasm retracts during fixation, yielding the "lacune" (space); so, we have a "large cell sitting in an empty space." Surrounding these cells are non-neoplastic lymphocytes. Other background cells that may be seen in other fields are plasma cells, histiocytes, eosinophils, and rarely neutrophils.
FYI: The RS cells elaborate a number of cytokines that attract non-neoplastic cells into the lymph node, then induce anergy in them, thereby escaping immune detection. These "stealth mechanisms" are shared by other tumors as well, including some carcinomas.
The lacunar cells show membrane and Golgi region reactivity for CD15 in this image. (Details: the stain for tissue is called "Leu M-1," and it targets the CD15 antigen, which is NORMALLY seen on neutrophils and some non-hematopoietic cells, but NEVER on B-cells--EXCEPT in Hodgkin's!!) The pattern of reactivity for CD30 is exactly the same as for CD15 in the RS cells and variants.
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