Clinical TNM System
Based on assessing the stage and spread of the tumor process.
- T (tumour) — size of the primary lesion.
- N (lymph nodules) — involvement of regional and distant lymph nodes.
- M (organ metastases) — presence of secondary deposits in other organs.
Grading features is specific to different locations and typically ranges from 1 to 3. Special clinical forms of carcinomas include:
- Microcarcinoma — diameter less than 1 cm or absence of invasion into the lamina propria of the mucosa (often found in the thyroid and breast).
- "Small cancer" — a term applied to small neoplasms of the stomach.
- Occult tumors — hidden lesions that produced no clinical manifestations and were not diagnosed during standard examination.
Morphological Criteria and Histogenesis
Morphology is the foundation of oncological diagnosis. Tumors are divided according to the degree of cellular maturity into benign, borderline, and malignant.
Depending on the source of origin (histo- and cytogenesis), epithelial neoplasms include:
- From surface epithelium (squamous and transitional): benign (papillomas) and malignant (squamous cell and transitional cell carcinoma).
- From glandular epithelium: benign (adenomas, adenomatous polyps) and malignant (adenocarcinomas, for which 3 levels of differentiation are distinguished).
Standard hematoxylin and eosin (H&E) staining is sufficient to determine histogenesis in most cases. If cells are poorly differentiated, special methods are used: immunohistochemistry (IHC), PCR, genome analysis, and electron microscopy.
Benign Epithelial Tumors
Papilloma — an organ-nonspecific tumor arising from the surface epithelium of the skin, mucous membranes (esophagus, vagina, urinary bladder), or bronchial tree. Externally, it has a papillary surface resembling cauliflower. Microscopically, it consists of epithelial proliferations with a fibrovascular core (connective tissue with blood vessels inside the papilla). The epithelium retains basement membrane integrity, polarity, cohesiveness, and stratification, though the number of layers increases (a sign of architectural atypia). It rarely undergoes malignant transformation, but is dangerous when localized in the larynx, urinary bladder, and skin. A variant with pronounced keratinization is called a keratoma.
Adenoma — forms from glandular tissue. It may grow outward as a finger-like projection or polyp (exophytic growth) or spread flat along the mucosa (flat adenoma with endophytic growth). Depending on the structures formed, tubular, trabecular, alveolar, papillary, and cystadenoma types are distinguished. If a developed stroma predominates in an adenoma, it is called a fibroadenoma (typical for the breast and ovaries).
Differentiation and Markers of Malignant Growth
The level of differentiation in malignant tumors is determined by three criteria: the expression of histogenesis markers, preservation of functional activity, and the degree of cellular atypia.
For example, well-differentiated squamous cell carcinoma preserves intercellular bridges and forms "cancer pearls" (extracellular keratinization). In moderately differentiated tumors, keratinization becomes intracellular, while in poorly differentiated tumors, it is virtually absent, leaving only stratification.
For precise identification of carcinomas, specific protein oncomarkers are sought using IHC:
- Group markers: cytokeratins.
- Organ-specific markers: thyroglobulin (thyroid gland), CEA (intestine), CA19-9 (ovaries), racemase and tyrosine (prostate gland).
- Neuroendocrine markers: chromogranins, synaptophysin, neuron-specific enolase (NSE), and CD57.
It is important to remember that IHC is an auxiliary method. Morphological verification remains primary, as metaplasia and transdifferentiation of cells can occur during tumor progression.