Immunohistochemical Characterization of Stromal Nodules in Benign Prostatic Hyperplasia

The goal of this study is to characterize stromal nodules in benign prostatic hyperplasia (BPH) in a Chinese population. BPH specimens were obtained by superpubic enucleation. Immunohistochemical staining for vimentin, muscle actin (HHF35), and smooth muscle actin (1A4) was conducted in serial sections of 55 consecutive stromal nodules of BPH specimens. The simplest stromal nodules were undifferentiated nodules that contained vimentin-negative and smooth muscle actin-negative cells. These cells were designated as undifferentiated mesenchymal cells. Immunohistochemical staining identified two cell types. Smooth muscle cells contained smooth muscle actin and vimentin, while fibrocytes contained vimentin but not smooth muscle actin. Fibrous nodules contained fibrocytes. Two more types of stromal nodules were fibromuscular nodules, which contained mixtures of fibrocytes and smooth muscle cells, and muscular nodules, which contained only smooth muscle cells. Of 55 stromal nodules, 11 (20%) were undifferentiated, 5 (9%) were fibrous, 37 (67%) were fibromuscular, and 2 (4%) were muscular.