SN1 SHORT NOTE 5M ★ High-yield

Define dysplasia and carcinoma in situ. Describe their features and significance.

Pathology · 2nd Professional — Para-Clinical

Definitions

Term	Definition
Dysplasia	Disordered growth with loss of uniformity and of architectural orientation; a pre-malignant change
Carcinoma IN situ	Full-thickness dysplasia involving the entire epithelium, but with the basement membrane still intact
Invasive carcinoma	Malignant cells have breached the basement membrane

Features of Dysplasia

Loss of uniformity of individual cells and loss of their architectural orientation
Pleomorphism — variation in size and shape
Hyperchromatic nuclei with a high nuclear:cytoplasmic ratio
Mitoses that are numerous and appear at all levels of the epithelium, not only in the basal layer
Loss of polarity — the orderly maturation from base to surface is lost
Graded as mild, moderate and severe by how much of the thickness is involved

Behaviour and Significance

Grade	Extent	Behaviour
Mild dysplasia (CIN 1)	Lower third of the epithelium	Usually regresses spontaneously
Moderate dysplasia (CIN 2)	Lower two-thirds	May regress, persist or progress
Severe dysplasia (CIN 3)	More than two-thirds	Usually progresses if untreated
Carcinoma IN situ	Full thickness; basement membrane intact	Progresses to invasion in most cases over years; but is curable by complete local excision

CLINICAL PEARL

Carcinoma in situ has no capacity to metastasise, and that is the whole point of screening. There are no lymphatics or blood vessels above the basement membrane, so however malignant the cells look, they cannot spread while it is intact. Detecting and removing the lesion at this stage is completely curative.

Common Sites

Cervix — the transformation zone; detected by the Pap smear; the model for cancer screening worldwide
Bronchus — in smokers, following squamous metaplasia
Oesophagus — in Barrett mucosa
Stomach — in chronic atrophic gastritis with intestinal metaplasia
Skin — solar (actinic) keratosis; Bowen disease is squamous carcinoma in situ
Breast — ductal and lobular carcinoma in situ
Oral cavity — leukoplakia and erythroplakia; especially important in India

Applied Aspects

Dysplasia is reversible if the stimulus is removed, particularly the milder grades — stopping smoking or tobacco chewing genuinely reverses early lesions
Cervical screening detects the pre-invasive stage and has reduced mortality dramatically wherever it is well organised; India's low coverage is the chief reason cervical cancer remains so common here
Cytology cannot distinguish in situ from invasive disease, since it shows cells without their architecture — a positive smear must always be followed by colposcopy and biopsy
Erythroplakia carries a much higher risk of malignancy than leukoplakia and must always be biopsied
Ductal carcinoma in situ of the breast is now found chiefly by mammographic microcalcification, and is treated by excision with clear margins

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