Histology

Norm Tissue without pathological changes, pathologist interpretation

Synonyms: biopsy, microscopic examination of tissue.

Fresh piece of tissue under examination

Histological examination helps in diagnosing oncological processes and investigating various systemic and local pathological processes. Pathologists can perform histological examinations on biopsy material and tissue samples taken during surgery. Accurate evaluations require pathologists to receive material from the pathological focus, not just general organ tissue. Obtaining material at the edge of the pathological focus is sometimes crucial (e.g., differentiating between tumor and normal tissue).

Histological material stored in paraffin blocks or fixed in formalin can undergo retrospective analysis. Flow cytometry can determine ploidy and tumor proliferation rate (S-phase) from formalin-fixed material stored for many years. However, some cytochemical reactions, estrogen and progesterone receptor determinations, and microbiological cultures cannot be performed on fixed material.

Place the material for histological examination in a fixative (formalin solution) that is 10-30 times the volume of the tissue sample. If performing an urgent histological examination with a frozen microtome, do not place the tissue in a fixative. Express histology with a frozen microtome is less accurate than fixed tissue histology. Surgeons typically use express histology during operations when making quick decisions about the extent of oncological intervention. An experienced specialist usually performs histological examinations. This examination has the highest diagnostic value and often forms the basis for a diagnosis.