Dysplasia

• is an abnormality of both differentiation and maturation
• dysplasia is a condition of disordered cell growth and proliferation which may arise de novo or from tissues already showing pathological hyperplasia, metaplasia, or chronic irritation and inflammation
• early stage dysplasia- reversible- if the stimulus is removed
• advanced dysplasia can progress to neoplasia- cancer

Most important microscopic features of dysplasia:

• Nuclear abnormalities -
  
• is characterized by increased size of nucleus (absolute and relative to the amount of cytoplasm)- increased nuclear/cytoplasmic ratio
• increased chromatin content
• abnormal chromatin distribution- coarse chromatin, clumping
• nuclear membrane abnormalities- thickening

• Cytoplasmic abnormalities -
• result from failure of normal differentiation, for example lack of mucin secretion (in glandular epithelium), lack of keratinization (in squamous epithelium)

• Increased rate of cell proliferation -
• is characterized by increased number of mitotic figures in many layers of epithelium (in contrast to the normal state in which mitoses are limited to basal and parabasal layers)
• mitoses are morphologically normal
• Disordered maturation -
  
• dysplastic epithelium resemble basal (stem) cells

• Grades of dysplasia - mild-moderate-severe

• epithelial dysplasia is premalignant lesion = lesion associated with higher risk of development of cancer = general term for invasive aggressive malignant tumor with potential to metastasize

Clinical examples of the dysplasia to neoplasia sequence:

1. Benign colorectal polyps (adenomas)- are composed of dysplastic epithelial glands-if left without surgical treatment- the majority of these will turn into malignant tumors
2. dysplasia in the uterine cervical epithelium- changes known as CIN- cervical intraepithelial neoplasia- if not treated- they will develop into maligant tumor
3. atypical hyperplasia, dysplasia and carcinoma- breast, uterine endometrium

The risk of developing the cancer depends on

• grade of dysplasia
• duration of d.
• site of dysplasia (d.in urinary bladder has high risk, d. of uterine cervix lower risk)

Differences between dysplasia and cancer

• differs in two important respects:

1. invasiveness
2. reversibility

• in dysplasia the abnormal cell proliferation does never invade the BM. Complete removal of dysplastic tissue is curative cancer in contrast, invades the BM and spreads through lymphatic and blood vessels, thus excision may not be curative
• reversibility- may sometimes return to normal- unlike cancer which is irreversible

Category: Pathology Notes