Due to the importance of arginase enzyme in different malignant disorders, the purpose of
the present study was to determine and compare the arginase activity in cancerous cells and
their normal and benign counterparts. The tissue arginase activity level was evaluated in 30
females with breast cancer, in 6 females with benign breast disease and in 9 healthy control
subjects. The arginase activity levels were significantly increased in malignant breast tissues in
comparison to healthy ones, while the difference did not reach the level of significance in
comparison to benign breast diseased tissues. Patients with advanced stage showed
insignificantly higher arginase activity compared to those with early stage. In addition,
estrogen receptor negative tumors showed insignificant higher arginase activ6ity levels
compared to estrogen receptor positive tumors. Moreover, tissues of premenopausal patients
showed lower activity levels of arginase compared with those of postmenopausal
ones.Meanwhile, patients with bad prognosis revealed insignificantly higher activity levels of
arginase compared to those with good prognosis. It could be concluded that tissue arginase
activity seems to be involved in the biological behaviour of breast cancer and its determination
in cancerous tissues could predict its outcome.