In normal immune system, the epithelioid cells are derived from:

Ref: Robbins Basic Pathology, E-book, P 85* Epithelioid cells are defined as cells that resemble epithelial cells (keratinocytes). They have large oval, pale, vesicular nuclei and abundant eosinophilic cytoplasm.* The best-known epithelioid cells are those derived from macrophages within granulomas, but tumor cells can also be described as epithelioid. Immunostaining may be needed to identify the type of epithelioid cell.MOST COMMON LESIONS WITH EPITHELIOID CELLS* Granulomas* Squamous cell carcinoma* Spitz nevus (spindle and epithelioid cell nevus)* Melanoma