GENETIC-ANALYSIS OF HYDATIDIFORM MOLES IN PARAFFIN WAX EMBEDDED TISSUE USING RAPID, SEQUENCE-SPECIFIC PCR-BASED HLA CLASS-II TYPING

Aims-To determine the applicability of rapid, sequence specific polyme rase chain reaction (PCR)-based HLA class II genotyping for the distin ction of complete from partial hydatidiform moles (HM) using DNA extra cted from formalin fixed and paraffin wax embedded tissue. Methods-Nin e HM were studied. DNA was extracted from formalin fixed and paraffin wax embedded tissue after mechanical separation of decidual and molar components. HLA class II DRB (DRB1, -3, -4, and -5) and DQB1 genotypin g was performed using a parallel series of PCR reactions, each of whic h contained sequence specific primers designed to amplify different HL A DRB and DQB1 alleles or allele groups (PCR-SSP analysis). In each ca se the HLA DRB and DQB1 genotypes identified within the decidua and HM were compared. Results-Within the decidual tissue, HLA DRB genotypes were assignable in all nine cases, and HLA DQB1 genotypes were identif ied in seven cases. Within the molar tissue, HLA DRB genotypes were as signable in seven cases, and at least one HLA DQB1 allele was identifi ed in seven cases. Interpretation based on HLA class II genotyping was therefore possible in two cases classified on histological appearance s as complete HM, in four classified as partial HM, and in one HM of u ncertain type. Different HLA DRB and DQB1 haplotypes were identified w ithin the decidual and molar tissue from both complete HM, consistent with a solely paternal origin and supporting the histological diagnosi s. HLA DRB and DQB1 alleles common to the decidual and molar tissue we re present within the four partial HM and the HM of histologically unc ertain type, consistent with combined maternal and paternal genetic in put to these HM, supporting the histological diagnosis in four cases a nd suggesting that the histologically equivocal case was also a partia l HM. Conclusion-PCR-SSP HLA class II DRB and DQB1 typing is reliably applicable to DNA extracted from formalin fixed and paraffin wax embed ded tissue. Therefore, in a suitably equipped HLA typing laboratory, t his technique provides a useful adjunct to histological examination fo r differentiation of complete from partial HM.