A previous study reported spontaneous development of hydronephrosis from ureteric obstructions caused by polypoid adenomas that localized from the renal pelvis to the ureter with severe cell infiltration and the appearance of Chil3l3/Ym1-positive crystals in acute myeloid leukemia of PML/RARα knock-in mice [7]. The gene discussed is RARA; the disease is acute myeloid leukemia.