The cytokeratins (Ker) and other types of intermediate filaments are routinely used as indicators of tumor cell types as well as markers of differentiation [3], because their composition in any particular epithelium is predictable [4] The presence of functional steroid receptors, estrogen receptor alpha and beta (ERα and ERβ), progesterone receptor A and B (PR-A and PR-B) has been quantitatively associated with histologic differentiation [5], response to therapy [6] and metastatic potential [7]. The gene discussed is RB1; the disease is neoplasm.