FOLDER 2.3 Clinical Correlation: Abnormal Duplication of Centrioles and Cancer ababFIGURE F2.3.1 • Multipolar mitotic spindle in a tumor cell. a. Electron micrograph of the invasive breast tumor cell showing abnormal symmetrical tripolar mitotic spindle in the metaphase of cell division. 16,000. b. This drawing composed by color tracings of microtubules (red), mitotic spindle poles (green), and metaphase chromosomes (blue) (obtained from six nonadja-cent serial sections of dividing tumor cell) shows more clearly the organization of this abnormal mitotic spindle. Detailed analy-sis and three-dimensional reconstruction of the spindle revealed that each spindle pole had at least two centrioles and that one spindle pole was composed of two distinct but adjacent foci of microtubules. (Reprinted with permission from Lingle WL. Salisbury JL. Altered centrosome structure is associated with abnormal mitoses in human breast tumors. Am J Path 1999; 155:1941–1951.) contain lipofuscin, which accumulates from the digestion of bacteria, foreign particles, dead cells, and their own organelles. Recent experiments indicate that lipofuscin accumulation may be an accurate indicator of cellular stress.
 Hemosiderin is an iron-storage complex found within the cytoplasm of many cells. It is most likely formed by the indigestible residues of hemoglobin, and its presence is related to phagocytosis of red blood cells. Hemosiderin is most easily demonstrated in the spleen, where aged erythrocytes are phagocytosed, but it can also be found in alveolar macrophages in the lung tissue, especially after pulmonary infection accompanied by small hemorrhage into the alveoli. It is visible in light microscopy as a deep brown granule, more or less indistinguishable from lipofuscin. Hemosiderin granules can be differentially stained using histochemical methods for iron detection.
 Glycogen is a highly branched polymer used as a storage material for glucose. It is not stained in the routine H&E preparation. However, it may be seen in the light microscope with special fixation and staining procedures (such as toluidine blue or the PAS method). Liver and striated muscle cells, which usually contain large amounts of glycogen, may display unstained regions where glycogen is located. Glycogen appears in EM as granules 25 to 30 nm in diameter or as clusters of granules that often occupy significant portions of the cytoplasm (Fig. 2.58).
 Lipid inclusions (fat droplets) are usually nutritive inclusions that provide energy for cellular metabolism. The lipid droplets may appear in a cell for a brief time (e.g., in intestinal absorptive cells) or may reside for a long period (e.g., in adipocytes). In adipocytes, lipid inclusions often constitute most of the cytoplasmic vol