1. The tumor cells are much rounded in shape compared to normal cells.
2. Mitochondrial size is said to be smaller in cancer cells than the normal. In cancer cells, the alternation is extremely frequent mitochondrial swelling and it appears denser. Some granules are smaller than mitochondria, termed as growth granules, which are found only in cancer cells.
3. Yoshida and Ehrlick showed that Golgi apparatus are greatly reduced in size in cancer cell. The mammary carcinoma of mice contains Brittner’s milk factor, which is virus like particles in the Golgi bodies.
4. Golgi bodies and centrosome actually determine the polarity of the cells. These are generally lost in cancer cells. Abnormal divisions of centrosome often give rise to multipolar spindle in cancer cells.
5. Some inclusions due to persistence of cellular activity are found in tumor cells, e.g., milk in adenocarcinoma in breast, colloid droplets in cytoplasm of thyroid cancer.
6. The nucleus is larger and nucleocytoplasmic ratio is altered. The nucleolus is also larger in size than normal cells.
7. Chromosomal abnormality is one of the most cytological changes that occurs in cancer cells. The tumor cells have an abnormal number of chromosomes, generally too many (aneuploidy). They often contain translocations. The first discovered Philadelphia chromosome was found in all hematopoietic cells with myelogeneous leukemia, where the chromosome results from a translocation between chromosome 9 and 22. Such translocation between chromosome 8 and 14 has also been observed in Burkitts lymphoma.
Another common chromosomal abnormality in tumor cells is the localized reduplication of DNA to produce as many as 100 copies in a given region. It may be tandemly organized at a single site or it may exist as small independent chromosome like structure. The former case leads to a homogeneously staining region (HSR) that is visible under the microscope.