Page 74 - Textbook of Pathology, 6th Edition

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SECTION I

Figure 3.45 Columnar metaplasia oesophagus (Barrett’s oeso-
phagus). Part of the oesophagus which is normally lined by squamous
epithelium undergoes metaplastic change to columnar epithelium of
intestinal type. Figure 3.46 Osseous metaplsia in leiomyoma uterus. The whorls
composed of the smooth muscle cells and fibroblasts show osseous
metaplasia in the centre.
iii) Conversion of pseudostratified ciliated columnar
epithelium in chronic bronchitis and bronchiectasis to 6. Nuclear hyperchromatism
columnar type. 7. Increased mitotic activity.
iv) In cervical erosion (congenital and adult type), there is The two most common examples of dysplastic changes
variable area of endocervical glandular mucosa everted into are the uterine cervix (Fig. 3.47) and respiratory tract.
the vagina. Dysplastic changes often occur due to chronic irritation
B. MESENCHYMAL METAPLASIA. Less often, there is or prolonged inflammation. On removal of the inciting
transformation of one adult type of mesenchymal tissue to stimulus, the changes may disappear. In a proportion of
General Pathology and Basic Techniques
another. The examples are as under: cases, however, dysplasia progresses into carcinoma in situ
1. Osseous metaplasia. Osseous metaplasia is formation of (cancer confined to layers superficial to basement membrane)
bone in fibrous tissue, cartilage and myxoid tissue. Examples or invasive cancer. This concept is further discussed again
of osseous metaplasia are as under: in details in Chapters 8, 17, and 24.
i) In arterial wall in old age (Mönckeberg’s medial calcific The differences between dysplasia and metaplasia are
sclerosis) contrasted in Table 3.7.
ii) In soft tissues in myositis ossificans
iii) In cartilage of larynx and bronchi in elderly people
iv) In scar of chronic inflammation of prolonged duration
v) In the fibrous stroma of tumour (Fig. 3.46).
2. Cartilaginous metaplasia. In healing of fractures,
cartilaginous metaplasia may occur where there is undue
mobility.
DYSPLASIA
Dysplasia means ‘disordered cellular development’, often
accompanied with metaplasia and hyperplasia; it is therefore
also referred to as atypical hyperplasia. Dysplasia occurs most
often in epithelial cells. Epithelial dysplasia is characterised
by cellular proliferation and cytologic changes. These changes
include:
1. Increased number of layers of epithelial cells
2. Disorderly arrangement of cells from basal layer to the
surface layer
3. Loss of basal polarity i.e. nuclei lying away from
basement membrane Figure 3.47 Uterine cervical dysplasia, high grade lesion. It shows
4. Cellular and nuclear pleomorphism increased number of layers of squamous epithelium having marked
5. Increased nucleocytoplasmic ratio cytologic atypia including mitoses.