Introduction
Benign epithelial tumours are subdivided by the epithelium they arise from: tumours of the integumentary (lining) epithelium are papillomas, tumours of glandular epithelium are adenomas.
Papillomas appear in stratified squamous epithelium, urothelium and galactophorous (milk) ducts; adenomas are tumours of glandular epithelium and of the mucosa of hollow organs. Examples: squamous cell papilloma (skin), adenomatous tubulovillous polyp, and fibroadenoma of the breast (a mixed fibroepithelial tumour).
Papillomas
A papilloma is a benign squamous epithelial tumour from skin and mucous membranes.
- Looks like a ledge or a bush of branching papillae (grossly like nodules); exophytic; slow growth.
- No capsule; a tree-like stroma covered by differentiated stratified squamous epithelium.
- Microscopically: the stroma lies in the middle of the tumour, covered by squamous or transitional epithelium; the base consists of connective tissue containing blood vessels, a continuation of the subepithelial connective tissue lined by epithelium.
- Firm or soft:
- Firm papillomas - on skin and mucous membranes (mouth, larynx, pharynx), lined by multilayered squamous epithelium.
- Soft papillomas - mainly in the neck of the urinary bladder and the region of the trigone (urinary tract), lined by cylindrical, transitional or ciliated epithelium. They have thin fibro-vascular cores with thin-walled vessels; the thin branching papillae are easily injured and bleed; they grow quickly.
- Papillomas of the urinary tract may become malignant.
- Bladder carcinoma: transitional epithelium papillomas are the most common (and sarcomas); painless haematuria.