There was no well-differentiated tumour in total PSA positive patients while 26.8% of the negative individuals experienced well-differentiated tumours, the difference was nearly significant. molecular forms of PSA existing in serum, that is, free (non-complexed) PSA and PSA complexed to 1-1-antichymotripsin. Recently, it has been shown that free PSA/total PSA percentage in prostate malignancy individuals is lower than individuals with benign prostatic hyperplasia and the percentage of free PSA enhances specificity and level of sensitivity of prostate malignancy analysis (Catalona em et al /em , 1995; T?rnblom em et al /em , 1999; Veltri and Miller, 1999). Cut-off ideals proposed for per cent free PSA have ranged from 17 to 25% (Kamoi and Babaian, 1999). Studies conducted in ladies with breast tumor revealed contrary results. It was shown that 44% of ladies with breast tumor and 58% of ladies with benign breast disease experienced serum free PSA as the major molecular form, whereas normal ladies had Aspartame PSA bound to 1-antichymotripsin as the major molecular form, and it Aspartame was suggested the ratio of free PSA/bound PSA might have value for analysis of breast diseases including breast tumor (Borchert em et al /em , 1997). In another study (Black em et al /em , 2000), it was shown the percentage (20%) of breast cancer individuals with free PSA as the predominant molecular form ( 50% of total PSA) in serum was significantly higher than that of healthy ladies (3%) or ladies with benign breast disease (4%), and it was stated that although free PSA as the predominant molecular form offers high specificity (96%), its medical utility is limited due to low level of sensitivity (20%). We concluded related results as with the study mentioned above (Black em et al /em , 2000), in our study. The percentage of free PSA predominant subjects (free PSA/total PSA 50%) in ladies with colorectal carcinoma was 20%, which was significantly higher than healthy ladies (3.3%). Even though sensitivity of free PSA predominancy was low (20%) in distinguishing ladies with colorectal carcinoma than healthy ladies, the specificity was higher (96.7%) which justifies further investigations to clarify its clinical significance. In our study, although serum total and free PSA levels were decreased as age improved both in ladies with colorectal carcinoma and healthy ladies, the correlations were not significant; the percentage of ladies more than 50 years was slightly reduced total PSA positive individuals than negatives. In one study serum total PSA levels were found to decrease significantly with ageing in both healthy women and ladies with breast tumor (Romppanen em et al /em , 1999). However, in another study no Aspartame significant correlation was found between serum total PSA levels and age in normal ladies while a negative correlation was shown in ladies with breast tumor (Borchert em et al /em , 1997). As with the explanation of the decrease of PSA manifestation with ageing in breast cancer cells (Yu em et al /em , 1994a), the decrease in PSA production with ageing might be due to the decrease of ovarian hormones which mediate PSA production by binding to the steroid receptors found in colorectal cancer cells. The cut-off ideals providing the specificity rate of 93.3% in our series, were 0.34?ng?ml?1 for total PSA and 0.01?ng?ml?1 for free PSA. The cut-off value in breast tumor analysis for total PSA is definitely 30?ng?ml?1 (Borchert em et al /em , 1997; Romppanen em et al /em , 1999) which is definitely 10 times lower than the value we found. This discrimination may be due to the difference in the sensitivities of PSA assays. With our cut-off values, Rabbit Polyclonal to STARD10 in our series, total PSA positivity was 20% and free PSA positivity was 34.6% in ladies with colorectal carcinoma. Having a cut-off value of 30?ng?ml?1 total PSA positivity rates were reported to be 6.5% (Borchert em et al /em , 1997) and 5.6% (Romppanen em et al /em , 1999) in women with breast cancer. We did not find any significant association with serum total PSA levels and the location, tumour size, depth of wall invasion or venous invasion. There was no well-differentiated tumour in.