Granular changes in vascular leiomyosarcoma

Summary

A 78-year-old male presented a tumor mass in the left arm which was surgically excised. Part of the tumor, when examined by light microscopy, showed the characteristic cytological features of a leiomyosarcoma. Other areas of neoplasm comprised layers of tumoral spindle-cells surrounding abnormal blood vessels. Nests of similar neoplastic cells were observed in the intima and media of these blood vessels. Wide areas of neoformation were made up by interlacing bundles of acidophilic polyedral cells with large irregular nucleus. Mitoses were frequent. The cytoplasm contained a great number of granules intensely PAS stained with and without prior diastase digestion. Electron microscopic examination revealed that the granular cells possessed a continuous basal lamina, numerous pinocytotic vesicles and abundant 80–150 Å microfilament bundles. Within the microfilament bundles, as well as apposed to the plasma membrane, electrondense bodies were often found. Granules contained degenerated organelles and probably corresponded to digestive vacuoles. In the intercellular spaces, fibrous long-spacing collagen was seen. The transition zone between the leiomyosarcoma cells and the granular cells showed intermediate cell types, with few granules and abundant microfilaments. The origin of granular cells from smooth muscle cells of blood vessels is discussed.