The development of many cancers and hematologic neoplasms is driven by neoplastic stem cells. These cells constitute a small proportion of the tumor mass and have low mitotic activity but demonstrate ability of efficient self-renewal.
It has long been recognized that many lymphomas and leukemias share phenotypic features with normal lymphocytes or their immature precursors. Realization of this fact provided a rationale for the classification of lymphomas and suggested their pathogenesis. Neoplastic transformation has been thought to occur at specific points during lymphoid development. The transformed cell becomes arrested at a certain stage of normal differentiation and this point corresponds to the event of malignant conversion.1 For example, lymphomas bearing the mature T-cell phenotype are supposed to result from the neoplastic transformation and clonal expansion of a single mature T cell. The same scheme has been applied for cutaneous lymphomas. It is widely accepted that the so-called primary cutaneous lymphomas originate directly from the lymphocytes recirculating through the skin, possibly from the lymphocytes belonging to the skin-associated lymphoid tissue.2,3 However, despite decades of research, this theory has not been experimentally confirmed and the nature of the initial steps of development of cutaneous lymphomas remains enigmatic.
Gniadecki R. Neoplastic Stem Cells in Cutaneous LymphomasEvidence and Clinical Implications. Arch Dermatol. 2004;140(9):1156-1160. doi:10.1001/archderm.140.9.1156