General Pathology:General Pathology:Cellular AdaptationsCellular Adaptations

Lorne Holland, M.D.Lorne.Holland@ucdenver.edu

Cellular AdaptationsCellular 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)

Hypertrophy- Hypertrophy- “too much “too much nourishment”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

Hyperplasia- Hyperplasia- “too much “too much growth”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

Hypertrophy and Hypertrophy and HyperplasiaHyperplasia

• 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

Atrophy- Atrophy- “no nourishment”“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

Hypoplasia- Hypoplasia- “little growth”“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

Metaplasia- Metaplasia- “changed “changed growth”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

Dysplasia- Dysplasia- “bad growth”“bad growth”

• Characterized by one or more– Hyperplasia especially with

increased mitotic figures– Decreased differentiation

Dysplasia- Dysplasia- “bad growth”“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

Neoplasia- Neoplasia- “new growth”“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)

CalcificationCalcification

• 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

AmyloidAmyloid

• 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

AmyloidosisAmyloidosis

• 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

AmyloidosisAmyloidosis

• 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

Questions?Questions?