Macroscopic picture
As a rule, the neoplasm appears as a single or multiple wart-like outgrowth. The shape may be spherical or slightly flattened. It is characterized by a broad base or a distinct stalk, which clearly demarcates the tumor from the surrounding healthy tissue.
The surface of the lesion is uneven—fine- or coarse-grained, which often makes the tumor look externally like cauliflower. The color varies from flesh-colored to grayish-brown or brown. On palpation, the node is soft, painless, and easily movable. There is no hair on the surface, but the covering epithelium may undergo keratinization and desquamate into dense scales. The tumor grows very slowly (over years) and is most often asymptomatic.
Histological structure and atypia
Since the neoplasm is benign, its cells retain the basic properties of the original tissue. Signs of typical squamous epithelium are clearly visible in the micropreparation:
- The integrity of the basement membrane is preserved (the tumor does not exhibit infiltrative growth and does not destroy underlying tissues).
- Normal polarity of epithelial cells is maintained.
- Stratification (clear layering of the epithelial sheet) and complexity are preserved.
The basis of each papilla is formed by a fibrovascular core, which is inward-growing connective tissue with nourishing blood vessels.
The main sign of the tumor process here is the presence of tissue atypia. It manifests as a significant increase in the number of epithelial layers in the proliferating papillas compared to the physiological norm. At the same time, cellular atypia (nuclear changes, pathological mitoses) is not characteristic.
Note: A variety of squamous cell papillomas with prominent keratinization processes are called keratomas.
Specific localizations
The tumor can arise on any body surface covered by the corresponding epithelium, but certain localizations have unique clinico-morphological features:
- Facial skin: is a true benign epidermal tumor. It occurs predominantly in elderly individuals with equal frequency in both sexes.
- Reproductive system: multiple squamous papillomas frequently form in the vagina, on the cervix, and the vulva. Vestibular forms (papillary outgrowths of loose connective tissue) develop in the vaginal vestibule, which is covered by stratified squamous non-keratinizing epithelium.
- Müllerian papilloma: a specific form found in children and young women. Microscopically, it presents as papillary outgrowths lined with Müllerian-type cuboidal cells. The tumor is benign, but tends to recur.
- Risk zones: localization in the larynx, on the mucosa of the urinary bladder, and on the skin requires oncological alertness, as the risk of cancer development in these areas is statistically higher.
Place in oncomorphological classification
To avoid confusing terms, it is necessary to clearly distinguish tumors by their source (histogenesis) and growth pattern.
According to morphological coding (ICD-O), several types of papillomas are distinguished: squamous cell (8052/0), inverted type squamous cell (8053/0), glandular (8260/0), and mixed (8560/0).
In the general classification of epithelial tumors, papilloma occupies the niche of benign neoplasms arising from the covering epithelium.
- If the tumor becomes malignant (destroys the basement membrane), it is classified as squamous cell carcinoma (carcinoma).
- If a benign tumor originates not from the covering epithelium, but from the glandular (secretory) epithelium, it is termed an adenoma (or cystadenoma if it has a cystic structure).
Imagine a papilloma as a hand in a thick winter glove. The "fingers" inside are the fibrovascular core (stroma with blood vessels). The "glove" itself is the epithelial sheet. The fact that the glove is unnaturally thick reflects tissue atypia (an increase in the number of cell layers). But as long as the glove fabric is intact and not torn down to the skin of the fingers, the basement membrane is preserved, which means the tumor is benign.
Class and exam questions
What is a fibrovascular core?
This is the central foundation of the tumor's papillary outgrowth. It consists of connective tissue containing blood vessels that nourish the proliferating epithelium.
What is the nature of atypia in a papilloma?
It is characterized only by tissue atypia: the number of epithelial cell layers in the papillae increases. There is no cellular atypia, and the basement membrane remains completely intact.
Which localizations of papillomas are considered the most dangerous?
The highest risk of malignant transformation (malignancy) is observed when the tumor is localized in the larynx, urinary bladder, and skin.
How to distinguish a papilloma from an adenoma?
Both tumors are benign, but a papilloma grows from the covering (usually squamous) epithelium, whereas an adenoma develops from the glandular (secretory) epithelium.
What else to study on this topic
- Condylomata acuminata: morphology and association with HPV
- Intraepithelial neoplasia (VIN) as a precancerous process
- Morphological classification of cancer (carcinoma) according to ICD-O
- Papillary hidradenoma: histogenesis and structure
- Causes and manifestations of vaginal adenosis
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