*9.1.6 Electron microscopy*

It helps in the diagnosis of poorly differentiated/undifferentiated cancers, which cannot identify the origin by light microscopy, for example, carcinomas show

desmosomes and specialized junctional complexes, structures that are not seen in sarcomas or lymphomas [27–29].

#### *9.1.7 Flow cytometry*

It quantitatively measures various individual cell characteristics, such as membrane antigens and the DNA content of tumor cells. Flow cytometry is useful for identification and classification of tumors of T and B lymphocytes (leukemias and lymphomas) and mononuclear-phagocytic cells.

Circulating tumor cells.

Detection, quantification, and characterization of rare solid tumor cells (e.g., carcinoma and melanoma) circulating in the blood are emerging as a diagnostic modality, although presently in the research stage. Few latest devices detect three-dimensional flow cells coated with antibodies specific for tumor cells of interest (e.g., carcinoma cells) in the blood.

It will be useful for early diagnosis, assessing the risk of metastasis, and assessing the response of tumor cells to therapy.

Tumor makers:

Tumor markers are products of malignant tumors that can be detected in the cells themselves or in blood and body fluids.

Usefulness


#### **9.2 Molecular profiling of tumors**

#### *9.2.1 Traditional cancer typing*

Traditionally cancer is diagnosed and classified according to the morphological (histopathology/ cytopathology) appearance of the cells and their surrounding tissue. It has limitations such as (i) relies on a subjective review of the tissue, which is dependent on the knowledge and experience of a pathologist, and, therefore, may not be reproducible, (ii) limited ability to determine the individual recurrence risk of cancer, (iii) insufficient to reflect the complicated underlying molecular events that drive the neoplastic process, and (iv) histopathology reports lack or offer very little information regarding the potential drug treatment regime to which cancer will respond. Traditional pathology reports help to determine treatment that leads to better outcomes. However, tumors with identical pathology may have different origins and respond differently to a treatment.
