Adenomas and risk of malignant transformation
Benign glandular tumors are capable of progressing into malignant neoplasms. Unlike papillomas, adenomas are characterized by:
- Dysplastic tissue changes.
- Appearance of foci of carcinoma in situ.
- High probability of malignant transformation with the formation of adenocarcinoma.
Squamous cell carcinoma
This malignant tumor forms in the same locations as papillomas. The source is progenitor cells of squamous epithelium or areas of its metaplasia.
Common localization:
- Skin, lungs, and larynx.
- Esophagus, cervix, and vagina.
- Urinary bladder.
Growth patterns:
- Carcinoma in situ (carcinoma in situ).
- Invasive squamous cell carcinoma.
Adenocarcinoma and its histological types
Adenocarcinoma is an organ-nonspecific malignant tumor developing from glandular epithelium (including areas of glandular metaplasia, e.g., in the esophagus).
Histological structure:
- Tubular — form tubular structures.
- Trabecular — form cords (trabeculae).
- Alveolar and papillary (frond-like).
- Cystadenomas — cystic formations.
Based on the degree of differentiation, well-, moderately, and poorly differentiated variants are distinguished.
Structural features and metastasis
Tumors are classified by the ratio of parenchyma to stroma:
- With poorly developed stroma: medullary and solid carcinoma.
- With developed stroma: scirrhous carcinoma (scirrhus).
A special variant is signet-ring cell carcinoma, whose cells accumulate mucus but do not form glands.
Metastasis: The main pathway of tumor cell dissemination is lymphogenous (to regional lymph nodes). Hematogenous metastases occur in later stages of the disease.
Briefly: answers to topical questions
What macroscopic growth patterns of cancer exist?
Macroscopic growth patterns of cancer include exophytic, endophytic, and mixed types.
- Exophytic growth — the tumor grows into the lumen of the intestine; plaque-like, polypoid, and coarsely nodular variants are distinguished.
- Endophytic growth — characterized by infiltrative growth, often accompanied by ulceration; ulcerated and diffusely infiltrative variants are distinguished.
- Mixed form — combines exophytic and endophytic growth with ulceration; an example is ulcerative (saucer-shaped) carcinoma.
Expansive, infiltrating, and appositional types of tumor growth are also distinguished.
What histological variants of squamous cell carcinoma are distinguished by the presence of keratinization?
Based on the presence of keratinization, two main histological variants of squamous cell carcinoma are distinguished.
| Sign | Keratinizing carcinoma | Non-keratinizing carcinoma |
|---|---|---|
| Cells | Form keratohyalin granules | Oval or polygonal, eosinophilic cytoplasm |
| Structures | Formation of "cancer pearls" | Intercellular bridges are usually not identified |
| Mitoses | Relatively rare | Frequent, including atypical ones |
Which organs are most characteristic of the development of scirrhous carcinoma?
The provided sources directly indicate the development of scirrhous carcinoma (scirrhus) in the stomach and intestine. Scirrhous carcinoma belongs to tumors with a developed stroma. In the stomach, it manifests as diffuse infiltrative carcinoma (linitis plastica), in which cells of the poorly differentiated tumor stop producing mucus and begin intensively synthesizing stromal collagen. Scirrhus is also mentioned in the classification of intestinal adenocarcinomas by the parenchyma-to-stroma ratio.
Which benign tumors develop from stratified squamous epithelium?
The following benign tumors and formations develop from stratified squamous epithelium:
- Papilloma — a tumor of the surface epithelium forming papillary proliferations with a fibrovascular core. The stratification, polarity, and cohesiveness of the squamous epithelium are preserved within it.
- Squamous papilloma — a variant of papilloma found in the vagina, vulva, and cervix.
- Keratoma — a papilloma originating from squamous epithelium with pronounced keratinization.
- Condyloma acuminata — a lesion in the form of papillary proliferations of fibrous stroma covered by stratified squamous epithelium.
What types of adenomas exist according to their microscopic structure?
According to their microscopic structure, several types of adenomas are distinguished:
- Tubular adenoma is represented by tubular structures.
- Villous adenoma consists of villous structures.
- Tubulovillous adenoma has a mixed structure.
- Fibroadenoma is a type of adenoma with a predominance of developed stroma (for example, the intracanalicular variant).
- Cystadenoma is a cystic variant of a benign epithelial tumor.
Cells in adenomas are characterized by immaturity, enlarged hyperchromatic nuclei, and pseudostratification.
What types of precancerous epithelial changes are distinguished?
The main types of precancerous epithelial changes include:
- Epithelial dysplasia (or intraepithelial neoplasia), a process associated with impaired cell maturation and the development of cellular atypia.
- Carcinoma in situ (carcinoma in situ).
- Atypical hyperplasia — for example, simple or complex atypical endometrial hyperplasia with a risk of malignant transformation.
- Leukoplakia with dysplasia, a precancerous change of squamous epithelium found in the oral cavity and on the vulva.
Precancerous conditions also include benign formations with a high risk of transformation, such as villous adenomas of the colon.
For adenoma, remember the sequence: Dysplasia -> Carcinoma in situ -> Malignant transformation to adenocarcinoma.
Class and exam questions
Which organ is a classic example of adenocarcinoma developing against the background of metaplasia?
A classic example is the development of adenocarcinoma against the background of glandular epithelial metaplasia in the esophagus.
What is the morphological feature of signet-ring cell carcinoma?
The cells of this special variant of adenocarcinoma contain a large amount of mucus, but they do not form glandular structures.
What is the main pathway of metastasis in adenocarcinoma?
The predominant pathway is lymphogenous, with the detection of the first metastases in regional lymph nodes.
What else to study on this topic
- Special variants of adenocarcinomas taking into account cytogenesis
- Classification of tumors by parenchymal-stromal ratio
- Differences between medullary and scirrhous carcinoma
- Morphological diagnosis of highly differentiated tubular endometrioid adenocarcinoma
- The role of cell precursors and metaplasia in tumor histogenesis
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