Three forms of cell death were found in human colon adenocarcinoma (HCAC), apoptosis, autophagy, and necrosis, by transmission electron microscopy. Apoptosis was characterized by chromatin hypercondensation and formation of apoptotic bodies, which were covered by plasma membrane. In autophagic cell death, autophagosomes of different complexities were observed along the process of cell degeneration which preceded nuclear collapse. In necrosis, cytoplasmic organelles, most notably mitochondria, were swollen, and plasma membrane was broken down causing the release of the cellular content into the extracellular space.