Inflammatory infiltration in cytology

Cytologic and histologic verification

For an accurate assessment of the nature of tissue lesions, histological examination of a biopsy specimen combined with cytologic study of an aspiration puncture remains the gold standard. This approach is critically important for differential diagnosis. Analysis of the cellular composition allows several main mechanisms of reactive changes accompanied by cell accumulation to be identified:

• Infiltration by classic inflammatory cells in infectious processes (lymphadenitis).
• Sinus histiocytosis — local accumulation and sharp increase in the number of macrophages.
• Accumulation of macrophages overloaded with metabolic products (observed in various storage diseases).
• Increase in the number of benign lymphocytes with the development of follicular or paracortical hyperplasia.

Cellular composition in lymphoid tissue lesions

Normally, peripheral organs of the immune system (lymph nodes, tonsils, Peyer's patches) have a clear division into T-zones (e.g., paracortex) and B-zones (germinal centers). Antigen-dependent cell differentiation takes place within them. Selective infiltration or lesion of a specific zone directly indicates a defect in the corresponding link.

In acute inflammation (reactive lymphadenitis), the tissue becomes permeated with serous exudate, and edema occurs. The swelling temporarily halts the outflow of peripheral lymph, which contributes to a massive accumulation of phagocytes and lymphocytes inside the lymph node to fulfill the barrier function. In the chronic stage, lymphoid infiltrates are gradually replaced by connective tissue.

A specific pattern of cellular infiltration is described in HIV infection at the stage of follicular hyperplasia:

1. In the paracortical zone, abundant diffuse infiltration by immunoblasts with high mitotic activity is detected.
2. Neutrophils and large mononuclear macrophages accumulate in the lumen of dilated sinuses.
3. At the final stage of this stage, multinucleated symplasts and desquamated endothelium appear, and the periphery of the follicles becomes densely populated by T-lymphocytes.

Infiltration in non-lymphoid organs

Accumulation of inflammatory-row cells is detected during cytologic and histologic analysis of pathologies of other systems:

• Uterine mucosa: in simple (glandular or glandular-cystic) endometrial hyperplasia, the stroma becomes rich in fibroblasts and lymphoid elements. Marked infiltration of the tissue by lymphocytes and neutrophils against the background of vascular congestion is characteristic (while cytologic atypia of the cells is absent, they retain proper orientation to the basement membrane).
• Myocardium: the inflammatory component plays a role in the progression of chronic diastolic heart failure. Working hypertrophy of cardiomyocytes is combined with stromal fibrosis and pronounced leukocytic infiltration. These changes lead to an increase in left ventricular end-diastolic pressure.
• Tissues in sarcoidosis: against the background of systemic immunological shifts (decrease in the number of T-lymphocytes, polyclonal B-cell activation), a specific granulomatous lesion occurs. In the end, this cellular granulomatous infiltrate is accompanied by the development of sclerotic processes that impair organ function.

Class and exam questions

What else to study on this topic

• Morphological stages of lymph node changes in HIV infection
• Histological forms and risk grades of endometrial hyperplasia
• Ultrastructural changes in cardiomyocytes during hypertrophy
• Mechanisms of decompensation of the hypertrophied myocardium
• Acute and chronic stages of reactive lymphadenitis

Other topics in the "Additional Topics" section

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