Epithelioid histiocytes (Epithelioid cells) are activated macrophages resembling epithelial cells:[1] elongated, with finely granular, pale eosinophilic (pink) cytoplasm and central, ovoid nucleus (oval or elongate), which is less dense than that of a lymphocyte. They have indistinct shape contour, often appear to merge into one another and can form aggregates known as giant cells.