Epitheloid cell is a modified –
**Core Concept**
Epithelioid cells are modified macrophages that play a significant role in granulomatous inflammation, particularly in conditions like tuberculosis and sarcoidosis. These cells are characterized by their large size, abundant cytoplasm, and often, a central nucleus. The transformation of macrophages into epithelioid cells is a hallmark of chronic inflammation.
**Why the Correct Answer is Right**
Epithelioid cells are derived from the differentiation of activated macrophages in response to chronic antigenic stimuli. This process involves the activation of various signaling pathways, including the NF-κB pathway, which leads to the upregulation of genes responsible for the transformation of macrophages into epithelioid cells. As a result, epithelioid cells acquire distinct morphological features, such as an abundant cytoplasm and a central nucleus, which distinguish them from their precursor macrophages.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because epithelioid cells are not derived from fibroblasts, although both cells can be involved in the formation of granulomas in different contexts.
**Option B:** This option is incorrect because dendritic cells are a distinct type of immune cell that plays a crucial role in antigen presentation, but they are not modified macrophages.
**Option C:** This option is incorrect because plasma cells are a type of immune cell that produces antibodies, but they are not modified macrophages.
**Clinical Pearl / High-Yield Fact**
In the context of granulomatous inflammation, the presence of epithelioid cells is a key diagnostic feature, and their detection can be aided by immunohistochemical staining for macrophage markers such as CD68.
**Correct Answer:** D. Modified macrophages.