Intramuscular angiomatosis of pelvic wall complicating pregnancy. Clinical, histological, and ultrastructural observations.

This is the first report of intramuscular angiomatosis involving the right bulbocavernous muscle in a pregnant woman, who underwent a cesarean section because of the risk of dystocia. The tumor was formed by well- and poorly differentiated vessels infiltrating the skeletal muscle fibers, which showed various degrees of degeneration. On electron microscopy, the neoplastic vessels were formed by large endothelial cells rich in organelles, limiting a luminal space and surrounded by a multilayered basal lamina. Pericytes were usually present around the endothelial layers. The neoplastic vascular structures seemed to grow by a process of gemmation. Our observations confirm the notion that this kind of benign neoplasm may pursue a rapidly growing course and presents a disturbing histological appearance which requires proper interpretation and precise diagnosis.