WEIGERT'S HEMATOXYLIN (A) , 500 mL

PRINCIPLE

The Papanicolaou test, named after Dr. Georgios Papanicolaou, a pioneer in cytology and cancer research, is performed to diagnose cervical cancer and cancers of other organs. It allows for the detection of cellular changes that may be precursors to cancer. In this technique, the first step involves staining nuclei with hematoxylins. The second step involves staining cytoplasms with an orange solution, which stains mature and keratinized cells with varying intensity. The third staining step uses the so-called polychromatic solution, which is a mixture of eosin, light green SF, and Bismarck brown. The polychromatic solution highlights the differentiation of simple squamous epithelium. Hematoxylin-Eosin staining is the most widely used in histology.

Hematoxylin dyes are primarily composed of metallic lakes of oxidized hematoxylin with divalent or trivalent ions. The staining mechanism involves covalent bonding of the metal-hematoxylin complex with anionic radicals of the tissue. In the case of nuclear material, the anionic groups of the DNA's phosphoric acid would be involved in the reaction. The selectivity of staining is enhanced by the acidic medium of the dye, as it hinders the coloration of amphoteric elements, such as the amino acids in proteins. The nuclei appear dark blue to violet.

Hematoxylin can be used for both progressive and regressive staining. In regressive staining, the nuclear structures are more differentiated and can be seen more clearly.