Characteristics and morphology of preneoplastic disorders

1. Concept

Preneoplastic (precancerous) lesions are acquired conditions that raise cancer risk; the hallmark reversible state is dysplasia. A precancerous lesion can stay stable, regress (if the stimulus is removed), or progress to cancer.

2. Classification

• Obligate — ~100% will become cancer (e.g. familial adenomatous polyposis, an AD hereditary cancer).
• Facultative — <100%; both genetic and environmental factors contribute.

3. Underlying drivers of precancerous states

Driver	Example → cancer
Increased regeneration	Cirrhosis → HCC; chronic skin fistula → SCC; Paget bone disease → osteosarcoma
Hyperplasia	Estrogen → endometrial hyperplasia → endometrial cancer; smoking → mucosal hyperplasia → metaplasia → dysplasia
Chronic inflammation/infection	ROS + cytokines: ulcerative colitis → colon cancer; H. pylori → gastric carcinoma
Immunodeficiency	AIDS → lymphoma; transplant → PTLD, skin cancers
Benign neoplasm	Adenomatous polyps → carcinoma

4. Morphology — dysplasia & CIN

Dysplasia: cellular atypia, increased/abnormal mitoses, loss of polarity, nuclear enlargement, not yet invasive.

Cervical intraepithelial neoplasia (CIN) — graded by how much epithelium undifferentiated basal cells replace:

• CIN1 = lower 1/3 (LSIL); CIN2 = 2/3; CIN3 = full thickness (carcinoma in situ; HSIL).
• Once cells breach the basement membrane → invasive carcinoma.

💡 High-yield: Precancer = dysplasia (reversible; can regress/progress). Obligate (FAP) vs facultative. Drivers: regeneration (cirrhosis→HCC), hyperplasia, chronic inflammation (UC→colon, H. pylori→gastric), immunodeficiency. CIN1/2/3 by epithelial thickness; BM breach = invasive carcinoma.