General Pathology: Cellular Adaptations

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General PathologyCellular Adaptations

• Lorne Holland, M.D.
• Lorne.Holland_at_ucdenver.edu

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Cellular Adaptations

• Given stressors, cells respond by changing their
  size, function or composition
• Some of these changes may be, at least initially,
  beneficial (hypertrophy, hyperplasia, metaplasia)
• Some of these changes are maladaptive (atrophy,
  hypoplasia)
• Left unchecked, some changes can ultimately lead
  to cancer (dysplasia)

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Hypertrophy- too much nourishment

• Increase in cell size without an increase in the
  number of cells
• Response to increased demand on a cell to do
  whatever it does
• Classic example- muscle cells in response to
  exercise
• Other examples- thyroid in response to hormonal
  stimulation during puberty
• Pathologic example- myocardial cells in response
  to chronic, systemic hypertension

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Hyperplasia- too much growth

• Increase in the number of cells without an
  increase in the size of cells
• Response to increased demand on a cell to do
  whatever it does
• Classic example- regenerating liver after
  damage/resection
• Other examples- glandular tissue in breast in
  response to puberty and pregnancy
• Pathologic example- endometrial tissue due to
  abnormal/irregular hormonal cycles

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Hypertrophy and Hyperplasia

• These processes do not have to occur separately
• Usually, both occur though one is by far more
  predominant
• Classic example- uterine smooth muscle during
  pregnancy

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Atrophy- no nourishment

• Decrease in organ size due to decreased cell size
  and/or decreased number of cells
• Physiologic- thymus in adulthood, uterus and
  testes in old age
• Pathologic- disuse, ischemia, starvation

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Hypoplasia- little growth

• Could be visually indistinguishable from atrophy
• Once normal or supernormal tissue which regresses
  is atrophic
• Tissue which never develops to normal size is
  hypoplastic
• Similar causes of hypoplasia as atrophy
• In the extreme, aplasia no growth usually due
  embryologic failure

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Metaplasia- changed growth

• Transformation of one normal cell type into
  another normal cells type
• Transition of ciliated glandular epithelium to
  squamous epithelium in respiratory tissue of
  smokers
• Transition of squamous epithelium to glandular
  epithelium in esophageal reflux
• Often, though not always a precursor to dysplasia

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Dysplasia- bad growth

• Characterized by one or more
• Hyperplasia especially with increased mitotic
  figures
• Decreased differentiation

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Dysplasia- bad growth

• Characterized by one or more (cont.)
• Atypia (not typical appearance)
• Pleomorphism (more forms)
• Variable cell size/shape
• Variable nucleus size/shape
• High nuclear to cytoplasm ratio
• Hyperchromasia (too much color) of nucleus

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Neoplasia- new growth

• Unregulated growth of abnormal tissue
• Commonly called a tumor (swelling)
• May or may not be cancer, depending on clinical
  behavior (malignant vs. benign)

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Calcification

• Abnormal precipitation of calcium in tissue
• Dystrophic due to wear and tear with normal
  blood calcium concentrations
• Atheromatous plaques
• Heart valves
• Fat necrosis
• Metastatic due to calcium in normal tissue with
  elevated blood calcium concentration
• Much less frequent but seen in hyperthyroidism,
  hypercalcemia of malignancy

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Amyloid

• Proteins which layer as B pleated sheets to form
  fibrillar structures
• Can be highlighted with special stains (Congo
  red)
• Small amounts can be seen in tissues of normal
  elderly people

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Amyloidosis

• AL amyloid
• Due to precipitation of immunoglobulin light
  chains produced by abnormal plasma cells
• AA amyloid
• Due to precipitation of serum amyloid protein A
  produced by liver during inflammation (acute
  phase reaction)
• Hereditary amyloidosis
• Due to genetic defects in proteins which favor
  precipitation

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Amyloidosis

• Can effect virtually any organ with clinical
  symptoms reflective of organ(s) most affected
• Predilection for affecting kidneys (filtering)
• Liver and spleen are also often enlarged

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Questions?