1 CASE REPORT In June 2009,a 29-year-old Chinese male was diagnosed as having Philadelphia chromosome-positive chronic myeloid leukemia (chronic phase);other than a high white blood cell count in peripheral blood (WBC,254.00×109/L) and splenomegaly,the patient exhibited no abnormal physical signs in mammary glands.He was given hydroxyurea for several days before he received treatment with 400 mg of imatinib mesylate daily.Two months later,the patient developed bilateral mastoplasia (fig.1) and retumed for further observation.His diffused enlarged lobules of mammary glands tissues were dilated at 5 cm in diameter,with tendess and stabbing pain,but no lactation,redness,edema,skin ruptures and infiltrations.B ultrasound examination of mammary glands showed mastoplasia without any masses.Based on the guideline of ELN (2009),the patient was evaluated to be in complete hematologic remission.He was screened for etiological factors,and progesterone,estradiol and prolactin levels were determined at 0.59 ng/mL,53.00 pg/mL and 10.04 ng/mL (normal of all),respectively.Moreover,both HbsAg and HCV-Ab were negative,and liver function was normal.The patient had no previous history of drug allergies and had not taken any other medications or special foods.