Renal cell cancer is a relatively common form of human cancer. Tumors develop in the kidney and have a tendency to grow into renal veins and metastasize to distant organs without the spread to regional lymph nodes as is common for many other tumor types.

This particular case shows a papillary form of renal cell cancer that grows with papillary excrescences into cyst formations and with areas of necrosis. The tumor has been stained with an antibody (HPA005785) that recognizes the CD44 protein.

CD44 is a cell-surface glycoprotein and a receptor for hyaluronic acid that is involved in cell-cell interactions, cell adhesion and migration. This protein participates in a wide variety of cellular functions including lymphocyte activation, recirculation and homing, hematopoiesis, and tumor metastasis. CD44 has, therefore, been suggested as a cancer stem cell marker. Elevated CD44 expression has been also associated with poor prognosis for patients with renal cell cancer.

The image shows papillary projections of tumor cells into a cyst-like structure to the left. All tumor cells display a strong positive membranous staining pattern. To the right there is a cyst with areas of necrosis and residual tumor cells. At the bottom we see a fibrous septa of tumor stroma that seperates the different cystic spaces.