Mucinous epithelial tumours arising from ovarian mature teratomas: a tissue genotyping study

Aims: The association of ovarian mucinous tumours with teratomas is well documented at tissue level, suggesting that some ovarian mucinous tumours arise from teratomas. Teratomas, being of germ cell origin, are genetically distinct from somatic cells, therefore providing a molecular basis for DNA genotyping to separate teratoma-derived mucinous tumours from metastatic ones. We assessed the diagnostic utility of DNA genotyping in ovarian mucinous tumours. Methods and results: Nine cases of ovarian mucinous borderline tumours and three mucinous carcinomas associated with teratomas were included, along with three mucinous tumours without associated teratoma for genotyping control. Target tissues (teratoma, mucinous tumour and paired normal tissue) were dissected microscopically, followed by genotyping at 15 short tandem repeat polymorphic loci. Of the 12 mucinous tumours with associated teratoma, tissue genotyping was informative in six cases, including four borderline tumours and two mucinous carcinomas. Homozygosity or partial homozygosity was observed in the teratomatous component in all six cases. Genotypical concordance between the teratoma and mucinous tumour was seen in five cases, including three borderline tumours and two mucinous carcinomas, suggesting clonal evolution. One mucinous borderline tumour showed an unmatched genotype with that of the corresponding teratoma, consistent with disparate tumour origins. All three mucinous tumours without teratoma displayed heterozygosity. Conclusions: When associated with a teratoma, ovarian mucinous tumours may arise frequently from the coexisting teratoma. In difficult cases, DNA genotyping may be used as a diagnostic tool in separating teratoma-derived primary ovarian mucinous tumours from those of somatic origin, particularly metastatic tumours from other sites.