Polyp cytology

Approaches to the diagnosis of polypoid lesions

Polypoid structures can form in various pathological processes, including tumor lesions of the respiratory tract and diseases of the reproductive system. In pulmonology, particularly in central (hilar) lung cancer developing in large bronchi against the background of chronic inflammation, polypoid, nodular, and branching macroscopic forms are distinguished. These changes are often preceded by precancerous conditions: squamous metaplasia and bronchial epithelial dysplasia. To verify the diagnosis in such cases, bronchoscopy with biopsy is used, alongside mandatory cytological examination of sputum.

In gynecology, cervical polyps require careful differential diagnosis. The primary method allowing them to be distinguished from Nabothian cysts, ectopy, erythroplakia, and endometriosis is colposcopy. At the same time, isolated cytological examination of smears or imprints has low informative value for assessing the epidermization process itself. However, it is an absolutely necessary step to exclude cellular atypia of the stratified squamous epithelium. If the colposcopic picture is unclear or dysplasia is suspected, the diagnosis is confirmed by histological verification (biopsy).

Cellular atypia and morphological markers

The key sign that a specialist looks for in a cytological specimen is cellular atypia. This condition, accompanying intraepithelial neoplasia, is characterized by a complex of specific changes in cell structure:

• Significant increase in the nuclear-cytoplasmic ratio.
• Nuclear hyperchromasia (intense staining).
• Pronounced nuclear polymorphism.
• Uneven chromatin distribution.

The pathological process is accompanied by impaired proliferation starting in the basal and parabasal layers of the epithelium. Immature cells begin to actively penetrate into the intermediate and superficial layers. Mitotic activity increases, and atypical mitoses may be recorded. Impaired differentiation and maturation of the epithelium is visualized as a loss of cellular polarity and general disorganization of the layered structure of the epithelial sheet.

HPV cytopathic effect: koilocyte morphology

In cytological specimens of stratified squamous epithelium, the specific effect of human papillomavirus, which has a proven absolute etiological role in the development of precancerous changes, is frequently detected. The main cytological marker of viral infection is the formation of koilocytes.

A typical koilocyte is an altered cell with the following characteristics:

• Large hyperchromatic nucleus containing coarse clumps of chromatin.
• Thickened and deformed (irregularly shaped) nuclear membrane.
• Presence of a wide rim of cleared cytoplasm around the nucleus—a perinuclear halo.

A clinically important nuance is the fact that koilocytes are characteristic of the episomal form of the virus (when particle assembly occurs inside the cell). As the infection progresses and transitions into the integrative form, when viral DNA is incorporated into the epithelial cell genome and triggers tumor transformation, morphological signs of koilocytosis disappear.

Cytological classification according to the Bethesda System (TBS)

To standardize the evaluation of cytological findings in international practice, the Bethesda System is used. It divides all squamous intraepithelial lesions into two major categories:

1. LSIL (low-grade squamous intraepithelial lesion) — this group includes isolated koilocytosis, mild dysplasia, and condylomas.
2. HSIL (high-grade squamous intraepithelial lesion) — combines moderate and severe dysplasia, as well as intraepithelial carcinoma (carcinoma in situ). This category is considered an obligate precancerous condition.

A similar approach is used in the WHO histological classification, which designates preinvasive lesions with the term SIL.

Histological grading of neoplasia

The severity of the pathological process (CIN) is determined by the depth of penetration of undifferentiated cells into the epithelial sheet (stratification):

• CIN I (mild): immature cells are confined to the lower third of the epithelial sheet. The upper layers remain mature.
• CIN II (moderate): abnormal cells occupy the lower two-thirds of the epithelial thickness. Signs of koilocytosis are less pronounced than in grade I.
• CIN III (severe and carcinoma in situ): dysplastic changes occupy more than two-thirds or the entire thickness of the epithelial sheet.

The most critical criterion for any intraepithelial neoplasia is the preservation of the basement membrane—tumor cells do not penetrate beyond it into the underlying stroma.

Class and exam questions

What else to study on this topic

• Macroscopic forms and histogenesis of central lung cancer
• Differential diagnosis of Nabothian cysts, ectopy, and erythroplakia during colposcopy
• Specific methods of visual tissue assessment (acetic acid test - VIA)
• Episomal and integrative forms of HPV existence in the cell
• Mechanisms of pulmonary complications in tumor growth (atelectasis, abscesses)

Other topics in the "Additional Topics" section

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