Stromelysin (ST)-3 is considered to be a marker of invasion and preinvasive lesions to indicate the likelihood of subsequent invasion. The expression of ST-3 has not been systematically studied in ovarian neoplasms. We studied 47 ovarian carcinomas and 49 ovarian tumours of low malignant potential (LMP) to see whether the expression of ST-3 correlated with any histopathologic features and, in the LMP tumours, whether its expression might be a prognostic indicator. All of the primary tumours and available metastases or implants were studied using immunohistochemistry (IHC) for ST-3 and, in 52 selected lesions, in situ hybridisation (ISH) using a cDNA probe. Expression of ST-3 was seen in 42 of 47 (89%) of the carcinomas and in 16 of 49 (33%) of the LMP cases. A significantly higher percentage of carcinomas than LMP tumours (P<0.00001) expressed ST-3 in the stroma adjacent to the tumour, with a correlation to increasing FIGO (International Federation of Gynecology and Obstetrics) tumour stage. ST-3 was expressed in the surrounding stroma of 1 of 8 LMP implants and 46 of 55 (84%) of the carcinoma metastases. The single LMP patient who died of tumour recurrence had ST-3 expression, but a significant prognostic impact was not found. The infrequent expression of ST-3 in LMP compared with carcinoma metastases appears to be more consistent with a peritoneal "field effect" than spread from the ovarian LMP tumour.
