The cystic areas in adamantinomatous craniopharyngioma are filled with dark thick fluid rich in proteins, blood, and cholesterol and with an appearance of "motor oil." When visualized with polarized light, this fluid shows gray, multilaminar, notched cholesterol crystals. Spillage of this cyst fluid in vivo during the surgical procedure may cause chemical meningitis. Courtesy of: Dr. Luciano de Souza Queiroz, Dept. of Pathology, Faculty of Medical Sciences, State University of Campinas (UNICAMP), Campinas, São Paulo State, BRAZIL. Additional images are here.