It is the study of tissue pathology by obtaining these tissues from the living or dead, by biopsy or surgical resection. It is the classic method of study, still the most useful one and has stood the test of time for over 100 years for definitive diagnosis of the disease.
Special studies or higher diagnostic modalities like special stains, Immunohistochemistry, Electron microscopy can be applied to routine histopathology in challenging situations and diagnostic dilemma.