We report a case of vascular leiomyoma of the bladder in a 62-year-old man. To our knowledge, this is the first ultrastructural study published on vascular leiomyoma of the bladder. The tumoral cells reproduced the smooth muscle cells. The vascular structures corresponded to capillaries and arterioles. We consider that the vascular component is not tumoral and its origin is related to mast cells.

The ultrastructural change in rat kidneys was analyzed after intraperitoneal injection of oxalic acid. This study demonstrates fundamental alterations in the epithelial cells of the proximal convoluted tubules (PCT). At 8 h (group IV), cytoplasmic prolongations (CP) begin to be observed, which fill the lumens of PCT at 20 h (group VII) and 24 h (group VIII). Unusual mechanism of cytoplasmic secretion is suggested to this fact. Calcium salts were found on CP and in group VIII. At 16 h (group IV), intracitoplasmic membranous structures (MS) appear, which can emigrate across the microvilli into the lumens of PCT. At 24 h (group VIII), MS are also shown in basal zone and in basement membrane. We considered that CP, which can fragment, and MS are the ultrastructural substratum of the matrix of the calculis, corresponding probably to the substance A.