Molecular biology in the diagnosis and prognosis of solid and lymphoid tumors

Applications of molecular testing in surgical pathology of the head and neck

Molecular testing in routine surgical pathology is becoming an important component of the workup of many different types of tumors. In fact, in some organ systems, guidelines now suggest that the standard of care is to obtain specific molecular panels for tumor classification and/or therapeutic planning. In the head and neck, clinically applicable molecular tests are not as abundant as in other organ systems. Most current head and neck biomarkers are utilized for diagnosis rather than as companion diagnostic tests to predict therapeutic response. As the number of potential molecular biomarker assays increases and cost pressures escalate, the pathologist must be able to navigate the molecular testing pathways. This review explores scenarios in which molecular testing might be beneficial and cost-effective in head and neck pathology.

Interphase cytogenetics in paraffin-embedded sections from renal cortical neoplasms. Correlation with cytogenetic and flow cytometric DNA ploidy analyses

Nonisotopic in situ hybridization (ISH) was performed on archival tissue sections from six renal cortical neoplasms and corresponding normal kidney tissue using pericentrometric (alpha-satellite) probes to chromosomes 1, 3, 7, 8, 10, 11, 12, 16, and 17. The results were correlated with classic cytogenetic analyses and flow cytometric DNA ploidy findings of these neoplasms. Our study shows that intratissue and intertissue ISH spot counts were generally homogeneous in normal kidney tissue and markedly heterogenous in tumor specimens. In all cases the correlation between the DNA Index and the ISH spot numbers was statistically significant. A correlation between modal and numerical chromosomal findings by cytogenetic analysis and ISH spot counts was found in three cases and was discordant in three cases. Our results also show that chromosomes 1, 3, 7, and 17 appear to manifest more propensity for aneuploidy than chromosomes 8, 10, 11, 12, and 16. We conclude that 1) numerical chromosomal aberrations by interphase in-situ hybridization correlate with DNA ploidy analysis in these tumors; 2) certain chromosomes may be more prone to aneuploidy than others; 3) determination of monosomy by ISH is less reliable on paraffin-embedded sections; and 4) the ISH technique complements conventional cytogenetic analysis in providing more information for the determination of cytogenetic aberrations and clonal heterogeneity in solid neoplasms.

Polymerase chain reaction-based restriction fragment length polymorphism analysis of the short arm of chromosome 3 in primary head and neck squamous carcinoma

BACKGROUND

Deletion or loss of heterozygosity (LOH) at the polymorphic loci on the short arm of chromosome 3 has been reported in a large number of renal cell, small cell lung, non-small cell lung, and cervical carcinomas, suggesting the presence of one or more putative tumor suppressor genes at chromosome 3p. Similar studies in primary head and neck carcinoma are lacking.

METHODS

To investigate the possibility of chromosome 3p deletions, the authors applied a polymerase chain reaction (PCR)-based, restriction fragment length polymorphism analysis, in conjunction with conventional Southern blot techniques, to DNA samples of matched normal mucosa and head and neck squamous cell carcinomas from 18 patients. The authors also assessed the merit of the PCR-based assay as a rapid screening tool, particularly in assaying limited tissue samples.

RESULTS

Constitutional heterozygosity at the polymorphic loci varied in the 18 normal samples that the authors studied: 12 at the D3F15S2 locus (on telomeric 3p21), 7 at the D3S32 locus (on centromeric 3p21), and 9 at the THRB locus (on 3p24). In 18 matched carcinoma specimens, LOH (deletion) was observed at D3S32 in 0 of 7, at D3F15S2 in 9 of 12 (75%), and at THRB in 3 of 9 cases (33%).

CONCLUSIONS

The results of the PCR-based assay and Southern blotting were completely concordant in all specimens the authors studied. This study indicates that deletion at 3p is a frequent abnormality in primary head and neck carcinoma and that the most common deletion region is telomeric to D3S32. The authors also observed an apparent correlation among poor histologic differentiation, DNA aneuploidy, and 3p deletions. Most poorly and moderately differentiated and aneuploid carcinomas manifested the 3p deletion. Therefore, the authors suggest an association between deletion at 3p and aggressive biologic behavior.

Familial and genetic aspects of colorectal carcinogenesis

There is abundant clinical and pathological evidence which suggests that colorectal cancer arises in a sequential manner through a series of events that can be followed during the progression of the disease from early adenoma through to metastatic disease. The molecular events that are associated with the initiation and progression of the disease are gradually being unravelled. As the molecular characterisation of colorectal cancer continues, new mechanisms by which the disease progresses are becoming evident. In this short review, a brief description of current knowledge of colorectal cancer development is presented.