Purpose of review: Molecular tools are used to refine the diagnosis of malignancy in pleural fluids. This review discusses the rationale and recent findings of the application of one of these tools, fluorescence in-situ hybridization, in pleural effusions.
Recent findings: Aneuploidy (i.e., pronounced numeric and structural chromosomal changes) is a recurrent finding in cells of solid tumors. Different methods attempt to detect tumor-associated aneuploidy to prove micrometastasis in different compartments, such as urine, cerebrospinal fluid, bone marrow, and body fluids. In recent years, fluorescence in-situ hybridization analysis has proved viable for detecting metastasis based on the observation of matching patterns of chromosomal aneusomies in primary tumors and corresponding metastasis.
Summary: Fluorescence in-situ hybridization analysis using specific probes for visualizing numeric aberrations in a microscopic evaluation (thus complementing routine cytologic evaluation) has been shown to be relatively simple, very robust, and thus applicable in material of lesser quality and more sensitive than routine cytology. Remarkably, dual-color fluorescence in-situ hybridization analysis allows for an efficient analysis in effusions, and the approach presented in this review proved to be more specific than other molecular procedures applied in effusions to detect malignancy, such as polymerase chain reaction. Prospective studies are needed to demonstrate that refinement of staging by fluorescence in-situ hybridization or polymerase chain reaction ('molecular upstaging') will translate into meaningful therapeutic consequences.