Variable expression in TLFCK can be seen for CK34βE12 (50%, 3/6 cases), NSE (50%, 2/4), PAX-2 (40.0%, 4/10), CD10 (33.3%, 7/21), HBME-1 (33.3%, 1/3), galectin-3 (33.3%, 1/3), CK20 (30.8%, 4/13), CD99 (25%, 1/4), CD15 (16.7%, 1/6), AMACR (9.1%, 1/11), RCC marker (8.3%, 1/12), CD56 (7.1%, 1/14), and WT-1 (6.7%, 1/15). The gene discussed is CD99; the disease is renal cell carcinoma.