Objective: Müllerian inclusion cysts (MIC) are small benign appearing glands that are occasionally noted in lymph nodes and peritoneal biopsies. They occur most frequently in women with serous ovarian tumors, with borderline tumors (SBOT) having a higher incidence than invasive cancers. The aim of this study was to examine whether MIC and SBOT have identical K-ras mutations, which would suggest that they are related. Methods. Six patients in whom adequate tissue was available from SBOT, MIC, and normal tissue were identified from a consecutive series of patients with SBOT who underwent lymph node sampling from 1992 to 1997 at Duke University Medical Center. DNA extraction was performed using laser capture microdissection. Exon 1 of the K-ras gene was amplified using PCR and subjected to single-strand conformation analysis to screen for mutations. Shifted bands were sequenced to confirm the presence of mutations.
Results: Mutations in codon 12 of K-ras were found in three of six (50%) SBOT. In two of these three cases, the identical mutation was found in the SBOT and the MIC (gly to val in both cases), but not in the corresponding normal DNA. In one case, a mutation was seen in the ovarian tumor (gly to asp), but not in the corresponding MIC.
Conclusions: Mutations in codon 12 of the K-ras gene are a hallmark of serous borderline tumors. The presence of identical K-ras mutations in some SBOT and their associated MIC suggests that they are related processes. Both may arise due to a field effect, or alternatively some MIC may represent metastases from the primary ovarian tumor.