Xanthoma: Yellowish firm nodules in the skin frequently indicating underlying disease, such as diabetes, disorder of fats (lipid disorder or hyperlipidemia), or other conditions. A xanthoma is a kind of harmless growth of tissue.
Under the microscope, a xanthoma can be seen to be composed of lipid-laden foam cells. These cells, termed histiocytes, contain lipid material in their cytoplasm (the nonnuclear zone of the cell).
The word "xanthoma" is made up of "xanth-" from the Greek roots "xanthos" (yellow) and "oma" (swelling) = a yellow swelling. A xanthoma is a circumscribed yellow swelling, a yellowish nodule.