Epithelioid Cells - Histology

What are Epithelioid Cells?

Epithelioid cells are a type of cell that resemble epithelial cells in their appearance and characteristics but are derived from other cell types, primarily macrophages. These cells are often found in granulomatous conditions and play a significant role in the immune response. They are characterized by their elongated shape, abundant cytoplasm, and presence in aggregates.

How are Epithelioid Cells Formed?

Epithelioid cells are formed through the transformation of monocytes into macrophages and subsequently into epithelioid cells. This process is typically triggered by chronic inflammation. The transformation is driven by various cytokines such as interferon-gamma (IFN-γ) and tumor necrosis factor-alpha (TNF-α), which promote the differentiation of macrophages into these specialized cells.

What is the Function of Epithelioid Cells?

The primary function of epithelioid cells is to participate in the formation of granulomas. Granulomas are organized collections of immune cells that form in response to persistent pathogens or irritants. Epithelioid cells contribute to the containment and isolation of these foreign substances, thereby preventing their spread. They also produce cytokines and enzymes that modulate the immune response.

Where are Epithelioid Cells Found?

Epithelioid cells are commonly found in granulomatous tissues. These tissues can be present in various diseases such as tuberculosis, sarcoidosis, and certain types of fungal infections. They are also observed in chronic inflammatory conditions and autoimmune diseases where persistent inflammatory stimuli are present.

How are Epithelioid Cells Identified in Histology?

In histological sections, epithelioid cells are identified based on their morphological characteristics. They appear as large, elongated cells with a high cytoplasm-to-nucleus ratio. The cytoplasm is often eosinophilic, and the nuclei can be oval or elongated. Special staining techniques, such as immunohistochemistry, can be used to identify specific markers like CD68 that are expressed by these cells.

What are the Clinical Implications of Epithelioid Cells?

The presence of epithelioid cells in tissue samples can be indicative of chronic inflammation or granulomatous disease. Their identification can aid in the diagnosis of conditions like tuberculosis, sarcoidosis, and other chronic inflammatory disorders. Additionally, the presence of these cells can provide insights into the stage and severity of the disease, guiding treatment decisions.

Conclusion

Epithelioid cells play a crucial role in the immune response, particularly in the formation of granulomas. Their identification in histological samples is essential for diagnosing various chronic inflammatory and granulomatous diseases. Understanding their formation, function, and clinical significance can greatly enhance diagnostic accuracy and therapeutic strategies in histopathology.