Goals:

• To help you begin to develop a systematic approach to studying pathologic specimens
• To help you recognize and understand common types of cell injury and adaptation

 

Learning Objectives:

• To use your knowledge of anatomy and histology to identify unknown gross specimens and histologic sections.
• To systematically identify and describe normal vs. pathologic tissue and lesions.
• To develop a differential diagnosis based upon your observations.
• To see pathologic injury in the context of a whole organ system or body (e.g. downstream effects).
• To begin to understand the cause and effects of ischemia, hypertension, and edema.
• To recognize and understand cellular adaptations including: hyperplasia, atrophy, hypertrophy, and metaplasia.
• To distinguish between reversible and irreversible injury.
• To differentiate (both conceptually and histologically) between apoptosis and necrosis.
• To understand adaptive changes such as steatosis and dystrophic calcification.
• To differentiate between intrinsic and extrinsic apoptosis.

 

Approaching pathologic specimens in a systematic way:

Examine the gross specimen:

What is the tissue/organ?

• Is there normal tissue present, and if so where is it?
• Can you find an edge or surface (e.g. pleural, serosal)?
• Does the size, shape, color, or texture help you determine the tissue type?

  (e.g. kidneys are kidney-shaped, lungs are spongy, the adrenals are yellow-orange)

Where is the pathology?

• Is the entire specimen pathologic?
• Is/are there discrete lesions (single, multiple)?
  • What are the size, shape, color, and texture of the lesions?
  • Are they uniform, solid, cavitary?
  • Are the lesion borders discrete or do they fade into the normal tissue?
  • What is the distribution?

    (e.g. medullary, cortical, perivascular, random, with the blood flow, on the serosal surface)

• If the pathology is diffuse, how do the shape, size, color, and texture of the organ differ from normal?

What might the lesions do to the normal functioning of the organ?

• Are they “space-occupying”?
• Do they obstruct normal structures?

  (e.g. blood vessels, airways, tubules, alveoli, ducts)

What might be the general effects to the patient?

• Might there be identical pathology in other organs?

  (e.g. miliary tuberculosis causes caseating granulomas through the body)

• Might there be related pathology in other organs?

  (e.g. compromise of the liver can cause jaundice of the skin and sclera)

How might the pathology be seen using other diagnostic modalities?

• What might it look like on an X-ray, a CT scan, an MRI?
• What lab tests might be affected?

  (e.g. lesions that block bile ducts causes serum levels of alkaline phosphatase to go up)

What might cause the pathology?

• Create a list of possibilities ranked according to probability (a differential diagnosis)

• VINDICATE
  • V - Vascular
  • I - Infection/Inflammatory/Auto-Immune
  • N - Neoplasm (Primary or Metastatic)
  • D - Drugs
  • I - Iatrogenic
  • C - Congenital/Developmental/Inherited
  • A - Anatomic
  • T - Trauma
  • E - Environmental Exposure/Endocrine/Metabolic

 

Examine the microscopic specimen:

What is it stained with?

• Most routine slides are stained with hematoxylin & eosin:
  • Hematoxylin stains acidic (negatively charged, basophilic) things blue/purple
  • Eosin stains basic (positively charged, acidophilic) things pink/red

Look at the specimen and very low power (if it is a glass slide, look at it without the microscope)?

• What color is it?
• Does it look like normal tissue from the organ that it was taken?

Look at the specimen at 10x?

• Does it match with your impression of the gross specimen?

  (e.g. does the lesion(s) appear diffuse, discrete, etc.)

• If the specimen is particularly blue or pink, what cells or substances are present?

  (e.g. inflammatory cells are blue, collagen/fibrosis is pink

Look at the specimen at 20x?

• What types of cells and structures are present?
• What should be there that isn’t?

  (e.g. normal parenchyma, patent blood vessels)

• What is there that shouldn't be?

  (e.g. inflammatory cells, tumor cells, bacteria, dead cells, bacteria, pigments, fat)

What other tests or special stains could you use do to help limit your differential diagnosis?

• (e.g. acid fast stain, PCR for gene rearrangement, immunohistochemistry)
•  

Integrate your gross & microscopic impressions and finalize your diagnosis!