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Epithelial Tumors

Q: What types of epithelial precancerous changes exist?

The main types of epithelial precancerous changes include: Epithelial dysplasia (or intraepithelial neoplasia) — a process associated with impaired cellular maturation and cellular atypia.Carcinoma in situ.Atypical hyperplasia — e.g., simple or complex atypical endometrial hyperplasia with a risk of malignant transformation.Leukoplakia with dysplasia — a precancerous change of squamous epithelium occurring in the oral cavity and vulva. Precancerous conditions also include benign lesions with a high transformation risk, such as villous adenomas of the colon.

Tumores epitheliales

For medical students2 min readUpdated 2026-10-10

Epithelial tumors arise from surface or glandular epithelium, as well as from progenitor cells and foci of metaplasia. They include benign neoplasms with a risk of malignant transformation and malignant forms, such as squamous cell carcinoma and adenocarcinoma.

Cells of originSurface and glandular epithelium, metaplasia

Adenoma riskHigh rate of malignant transformation into adenocarcinoma

Metastasis routesPredominantly lymphatic, less commonly hematogenous

Adenocarcinoma architectureTubular, trabecular, alveolar, papillary

Adenomas and Risk of Malignant Transformation

Benign glandular tumors can progress into malignant neoplasms. Unlike papillomas, adenomas are characterized by:

Dysplastic tissue changes.
Appearance of foci of carcinoma in situ.
High probability of malignant transformation into adenocarcinoma.

Squamous Cell Carcinoma

This malignant tumor develops in the same locations as papillomas. The source of origin includes squamous progenitor cells or areas of squamous metaplasia.

Common locations:

Skin, lungs, and larynx.
Esophagus, cervix, and vagina.
Urinary bladder.

Growth patterns:

Carcinoma in situ.
Invasive squamous cell carcinoma.

Adenocarcinoma and Its Histological Types

Adenocarcinoma is an organ-nonspecific malignant tumor originating from glandular epithelium (including areas of glandular metaplasia, such as in the esophagus).

Histological structure:

Tubular — forming tubular structures.
Trabecular — forming cords/trabeculae.
Alveolar and papillary.
Cystadenoma — cystic formations.

Based on the degree of differentiation, variants are classified as well-differentiated, moderately differentiated, and poorly differentiated.

Structural Features and Metastasis

Tumors are classified according to the parenchymal-to-stromal ratio:

Scant stroma: medullary and solid carcinoma.
Abundant stroma: scirrhous carcinoma (scirrhus).

A special variant is signet-ring cell carcinoma, whose cells accumulate mucin but do not form glands.

Metastasis: The primary route of tumor cell dissemination is lymphatic (to regional lymph nodes). Hematogenous metastases occur in later stages of the disease.

Mnemonic

For adenoma recall the sequence: Dysplasia -> Carcinoma in situ -> Malignant transformation into adenocarcinoma.

Frequently asked questions

What are the macroscopic growth patterns of carcinoma?

Macroscopic growth patterns include exophytic, endophytic, and mixed types.

Exophytic growth — tumor grows into the lumen; plaque-like, polypoid, and large nodular variants are distinguished.
Endophytic growth — characterized by infiltrative growth, often accompanied by ulceration; ulcerated and diffuse-infiltrative variants are distinguished.
Mixed form — combines exo- and endophytic growth with ulceration; an example is ulcerating carcinoma (crater-like).

Expansive, infiltrative, and appositional types of tumor growth are also recognized.

What histological variants of squamous cell carcinoma are distinguished based on keratinization?

Based on keratinization, two main histological variants of squamous cell carcinoma are distinguished.

Feature	Keratinizing carcinoma	Non-keratinizing carcinoma
Cells	Form keratohyalin granules	Oval or polygonal, eosinophilic cytoplasm
Structures	Form "keratin pearls"	Intercellular bridges are usually absent
Mitoses	Relatively infrequent	Frequent, including atypical ones

Which organs are most commonly affected by scirrhous carcinoma?

Scirrhous carcinoma (scirrhus) classically develops in the stomach and intestines. Scirrhous carcinoma belongs to tumors with abundant stroma. In the stomach, it manifests as diffuse-infiltrative carcinoma (linitis plastica), in which poorly differentiated tumor cells stop producing mucus and begin intensively synthesizing stromal collagen. Scirrhus is also mentioned in the classification of intestinal adenocarcinomas based on the parenchymal-stromal ratio.

Which benign tumors develop from stratified squamous epithelium?

The following benign tumors and lesions develop from stratified squamous epithelium:

Papilloma — a tumor of surface epithelium forming papillary projections with a fibrovascular core, retaining the stratification, polarity, and architectural integrity of squamous epithelium.
Squamous papilloma — a variant of papilloma found in the vagina, vulva, and cervix.
Keratoma — a papilloma from squamous epithelium with prominent keratinization.
Condyloma acuminatum — a lesion consisting of papillary projections of fibrous stroma covered by stratified squamous epithelium.

What types of adenomas exist based on microscopic structure?

Based on microscopic structure, several types of adenomas are distinguished:

Tubular adenoma — composed of tubular structures.
Villous adenoma — composed of villous structures.
Tubulovillous adenoma — has a mixed structure.
Fibroadenoma — a variant of adenoma with a predominance of abundant stroma (e.g., intracanalicular variant).
Cystadenoma — a cystic variant of benign epithelial tumor.

Cells in adenomas are characterized by immaturity, enlarged hyperchromatic nuclei, and pseudostratification.

What types of epithelial precancerous changes exist?

The main types of epithelial precancerous changes include:

Epithelial dysplasia (or intraepithelial neoplasia) — a process associated with impaired cellular maturation and cellular atypia.
Carcinoma in situ.
Atypical hyperplasia — e.g., simple or complex atypical endometrial hyperplasia with a risk of malignant transformation.
Leukoplakia with dysplasia — a precancerous change of squamous epithelium occurring in the oral cavity and vulva.

Precancerous conditions also include benign lesions with a high transformation risk, such as villous adenomas of the colon.

What organ serves as a classic example of adenocarcinoma developing on the background of metaplasia?

A classic example is the development of adenocarcinoma on the background of glandular metaplasia of the esophageal epithelium (Barrett esophagus).

What is the morphological feature of signet-ring cell carcinoma?

The cells of this special variant of adenocarcinoma contain large amounts of mucin, yet they do not form glandular structures.

What is the primary route of metastasis for adenocarcinoma?

The predominant route is lymphatic, with the first metastases found in regional lymph nodes.

Go deeper

Special variants of adenocarcinomas considering cytogenesis
Tumor classification by parenchymal-to-stromal ratio
Differences between medullary and scirrhous carcinoma
Morphological diagnosis of well-differentiated tubular endometrioid adenocarcinoma
Role of progenitor cells and metaplasia in tumor histogenesis