Submucosal myomas of the uterus are made-up of smooth muscle cells of the highly differentiated contractile phenotype (alpha-SMA- and desmin-immunoreactivity), as well as smooth muscle cell of the synthetic phenotype which proliferate (alpha-SMA-, vimentin- and PCNA-immunoreactivity). In submucosal myoma of the uterus there is a significant presence of connective tissue as a result of synthetic activity of fibroblasts, which clearly differ in their immunocytochemical characteristics from smooth muscle cells of the synthetic phenotype.