Pleomorphism is a term used in histology and cytopathology to describe variability in the size, shape and staining of cells and/or their nuclei. Several key determinants of cell and nuclear size, like ploidy and the regulation of cellular metabolism, are commonly disrupted in tumors.[1] Therefore, cellular and nuclear pleomorphism is one of the earliest hallmarks of cancer progression and a feature characteristic of malignant neoplasms and dysplasia.[2][3] Certain benign cell types may also exhibit pleomorphism, e.g. neuroendocrine cells, Arias-Stella reaction.
A rare type of rhabdomyosarcoma that is found in adults is known as pleomorphic rhabdomyosarcoma.[4]
Despite the prevalence of pleomorphism in human pathology, its role in disease progression is unclear. In epithelial tissue, pleomorphism in cellular size can induce packing defects and disperse aberrant cells.[5] But the consequence of atypical cell and nuclear morphology in other tissues is unknown.