*9.1.3 Cytological examination*

It is performed on many tissues and is usually done for identifying neoplastic cells. Methods of obtaining cells.

Exfoliative cytology: It is the study of spontaneously exfoliated (shed) cells from the lining of an organ into a body cavity.

Fine-needle aspiration cytology.

It involves aspiration of cells and attendant fluid with a small-bore needle. The smears are prepared and stained, followed by microscopic examination of cells. It is a widely-used simple and quick procedure.

Liquid-based cytology (thin prep): This is a special technique for preparation of samples that provides uniform monolayered dispersion of cells on smears.

Cytological characteristics of cancer cells:

Cancer cells have decreased cohesiveness and show cellular features of anaplasia. Cytological, differentiation can be made between normal, dysplastic, carcinoma in situ, and malignant cells.

Disadvantages of cytological examination:

Diagnosis is based on the features of individual cells or a clump of cells, without the supporting evidence of loss of orientation.

The invasion that is diagnostic of malignant tumor under histology cannot be assessed by cytology [27–29].

#### *9.1.4 Histochemistry and cytochemistry*

These are stains, which identify the chemical nature of cell contents or their products. H&E staining cannot demonstrate certain specific substances/constituents of cells. This requires some special stains. Common histochemical and cytochemical stains useful in diagnosis of tumors are listed in

Immunohistochemistry:-

It is an immunological method of identifying the antigenic component in the cell or one of its components by using specific antibodies. It is widely used in the diagnosis or management of malignant neoplasms.

Uses of Immunohistochemistry:-
