Readers' Responses to "Cancer of Unknown Primary Site: Advances in Diagnostics"

agnostic tools used to attempt to identify the primary site of carcinomas, including immunohistochemistry, and acknowledge the limitations of these techniques. 1 They also highlight the recent development of molecular diagnostic tools such as genomic microarray-based Pathwork Tissue of Origin test by Pathwork Diagnostics, using reverse transcription–polymerase chain reaction (RT-PCR)–based assays on paraffin-embedded tissue, which may hopefully enhance diagnostic capabilities, in order to impact on therapeutic decision making. 2 We wish to also highlight the development of microRNA analysis, recently reported at the American Society of Clinical Oncology annual meeting, as an additional tool to aid in molecular diagnosis of cancers of unknown primary site, and propose its availability to the oncologic community at large. Also using RT-PCR, the authors used 22-oligonucleotide RNA molecules (microRNA) involved in gene expression regulation to evaluate RNA extracted from tumors from patients with cancer of unknown primary, and demonstrated concordance (full and plausible) with the actual clinical presentation in 82% of cases. 3 These small RNA molecules have been shown to be highly effective biomarkers, with high tissue specificity, and are more stable for use on formalin-fixed paraffin-embedded block tissue, as well as fine-needle aspiration