Localized fibrosis of the corpus cavernosum: an example of fibrosis arising from the vascular smooth muscle cells. Report of a case with histogenetic considerations

We report a rare case of a localized fibrosis of the corpus cavernosum (CC) presenting as a nodular mass in the dorsal region of the penis without abnormal curvature of the organ. Histological and immunohistochemical examination revealed a fibrotic process, involving CC but not tunica albuginea, arising from the smooth muscle cells of the vascular channels. Two different morphological phases were identified in these vascular lesions: proliferative and residual phase. The proliferative phase was characterized by hyperplasia and moderate fibrous thickness of the smooth muscle layer of the vascular channels of CC, resulting with the formation of concentric perivascular cuffs and nodules. The residual phase was characterized by a progressive nodular fibrotic transformation with narrowing of the original vascular channels and replacement of the normal CC structures. The cells of this phase exhibited an immunophenotype of both fibroblasts (vimentin+; alpha-smooth muscle actin-) and myofibroblasts (vimentin+; alpha-smooth muscle actin+). The clinicopathological features of the lesion and histogenetic considerations are discussed.