Immunohistological analysis of stress-induced phosphoprotein 1 in ovarian cancer patients with low serum cancer antigen 125 levels.

OBJECTIVE

Stress-induced phosphoprotein 1 (STIP1) was recently identified as a potential tumor marker for human ovarian cancer. This study further evaluates the usefulness of STIP1 in ovarian tumor patients with normal CA125 serum levels.

MATERIALS AND METHODS

STIP1 and CA125 were immunohistochemically analyzed in 84 primary ovarian cancer and 30 benign ovarian tumors in patients with serum CA125 levels < 35 U/mL before surgery. Histoscores (0-300) were calculated as staining intensities (0-3) multiplied by percentage of tumor tissue (0-100%).

RESULTS

The cell types of the 84 cancers included 11 serous, 10 clear-cell, 51 mucinous, and 12 endometrioid carcinomas. There were 55 patients with invasive cancer and 29 with borderline ovarian tumors. The histoscores of STIP1, but not of CA125, in invasive cancer (mean ± SD, 186.3 ± 82.5) were significantly (p < 0.0001) higher than those seen in borderline ovarian tumors (86.2 ± 85.5). When the STIP1 histoscore was set at 183.8, invasive cancers (n = 55) were identified from benign tumors (n = 30) with a sensitivity of 56.4%, a specificity of 93.3%, a positive predictive value of 93.9%, and a negative predictive value of 53.8%. Results of receiver operating characteristics analysis showed that the area under curve of the STIP1 histoscore was 0.755, which was superior to that of CA125 (0.599).

CONCLUSION

STIP1 histoscores may be useful in detecting invasive human ovarian cancer in patients with low serum CA125 levels.