DEFINITIONS OF PATHOLOGY

1. The study of the essential nature of disease, including symptoms/signs, pathogens, complications, and morphologic consequences including structural and functional alterations in cells, tissues, and organs.
2. The study of all aspects of the disease process focusing on the pathogenesis leading to classical structural changes (gross and histopathology) as well as molecular alteration

OVERVIEW OF PATHOLOGY

1. Etiology (cause)
a. Genetic
b. Acquired
2. Pathogenesis: temporal sequence and patterns of cellular injury that lead to disease
3. Morphologic changes of t h e disease process
a. Gross changes
b. Microscopic changes
4. Clinical significance
a. Signs and symptoms of specific diseases
b. Disease course—complications
c. Prognosis

METHODS USED IN PATHOLOGY

1. Gross examination of organs
a. Gross examination of organs on exam questions has two major components:

i. Identifying the organ
ii. Identifying the pathology

b. Useful gross features

i. Size
ii. Shape
iii. Consistency
iv. Color

2. Microscopic examination of tissue

a. Light microscopy
Common denominator: Hematoxylin binds nucleic acids and calcium salts, while eosin stains
the majority of proteins (both extracellular and intracellular).
b. Other histochemical stains (chemical reactions)
i. Prussian blue—iron
ii. Congo red—amyloid
iii. Acid fast (Ziel-Neelson, Pite)—acid-fast bacilli
iv. Periodic acid-Schiff (PAS)—with high carbohydrate content molecules
v. Gram stain—bacteria
vi. Trichrome—cells and connective tissue
vii. Reticulin—collagen type III molecules
c. Immunohistochemical (antibody) stains
i. Cytokeratin—epithelial cells
ii. Vimentin—cells of mesenchymal origin except the three muscle types; stains
many sarcomas
iii. Desmin—smooth, cardiac, and skeletal myosin
iv. Prostate specific antigen (PSA)
v. Many others
3. Ancillary techniques
a. Immunofluorescence microscopy (IFM) is typically used for:
i. Renal diseases
ii. Autoimmune diseases
b. Transmission electron microscopy (EM) is typically used for:
i. Renal disease
ii. Neoplasms
iii. Infections
iv. Genetic disorders
4, Molecular techniques
a. Protein electrophoresis
b. Southern and Western blots
c. Polymerase chain reaction (PCR)
d. Cytogenetic analysis, e.g., karyotyping, in situ hybridization studies
i. Hematoxylin and eosin (H&E)—gold standard stain