Molecular biological techniques as a tool in diagnostic pathology : Applications in B-cell lymphoproliferative disease, medullary thyroid carcinoma and cervical carcinoma

Abstract: Identification of malignancy associated with mutations in gene sequences requires detection ofas little as a single base difference. A powerful technique in mutation detection is polymerasechain reaction (PCR) followed by single-strand conformational polymorphism (SSCP) andsequencing.The present investigation is focused on improving tests for the following diagnostic questions:(i) clonality in malignancy of lymphoid origin by developing simple laboratory methodsbased on PCR in which the monoclonal B-cell lineage can be distinguished from thepolyclonal, (ii) presence of mutations in RET proto-oncogene involved in sporadic medullarythyroid carcinoma (MTC), and (iii) development of a simple test which can distinguishbetween prototype human papillomavirus 16 (HPV16) and variant HPV16 containing a pointmutation at codon 83 of the E6 gene.The rearrangement of the immunoglobulin heavy chain gene can be used as a marker of B-celllineage and clonality. By using PCR with specific primers corresponding to the variable and joining regions, it is possible to detect the rearrangement of a small amount of clonal B-cells ina polyclonal background. This study has shown that the SSCP analysis of PCR fragmentsincreases the sensitivity and the specificity of the test.Oncogenic activation of the RET related to somatic missense mutations has been shown insporadic MTC. These mutations are believed to play an important role in the tumorigenesis ofMTC. By combining microdissection of tumor cells followed by PCR-SSCP, fragment sizeanalysis and sequencing, a small proportion of cells with mutation in a subpopulation of cellswithin a tumor can be detected. A variant of HPV 16 has previously been shown to be moreprevalent in invasive cervical carcinoma than in preinvasive lesions. In the present study asimple, rapid PCR-SSCP assay has been developed to identify women who are at increasedrisk of progression to invasive cervical carcinoma.