CD10, also known as common acute lymphoblastic leukemia (CALLA), has been shown to react with B and T lymphoblastic leukemia/lymphoma, follicular lymphoma, Burkitt’s lymphoma, and diffuse large B-cell lymphoma (1-3). CD10 has also been a very important marker in a panel, including CD20, CD5, CD23, cyclin D1, SOX11, BCL6 among others, to differentiate between small lymphoid cell lymphomas such as mantle cell lymphoma, follicular lymphoma, marginal zone lymphoma and small lymphocytic lymphoma (1-3). Studies have also shown that CD10 marks normal early lymphoid progenitors, immature B-cells in bone marrow, and germinal center cells in normal tonsil. It is also expressed in some non-lymphoid tissues such as fibroblasts, breast myoepithelium, and brush border and distal tubules of the kidney (1-3). CD10 has been shown to be expressed in clear cell renal cell carcinomas and may be a useful marker pointing to a renal source of carcinomas (4).