Virtually all malignant mesotheliomas (MMs) exhibit clonal chromosomal aberrations. Although the chromosome regions affected by these aberration(s) may vary from 1 tumor to another, certain regions are commonly disrupted. These aberrations are absent in benign mesothelial cells, and therefore their presence can be used to confirm a diagnosis of MM. In the current study, the authors investigated the value of karyotyping and fluorescence in situ hybridization (FISH) as adjuncts to conventional cytologic examination in patients with MM.
A retrospective analysis of 48 pleural or peritoneal fluids from patients with histologically confirmed MM was performed. Karyotypic analyses were attempted in all cases. In 27 cases, FISH for deletions of 9p21 (CDKN2A gene) and 22q was also performed because the karyotype was normal or unsuccessful.
Karyotypes were obtained in 35 (73%) of the specimens. Of these, 15 (43%) were abnormal and 20 (57%) were normal. Thirteen additional abnormal results were detected by FISH in cases for which the karyotypes were normal or unsuccessful. A total of 24 cases (50%) had an associated cytologic interpretation. Karyotyping or FISH was abnormal in 8 cases that were interpreted cytologically as either negative or suspicious.
The combination of FISH and karyotyping was found to improve on the diagnostic sensitivity of karyotyping alone in detecting MM in effusions. The authors concluded that karyotyping and FISH together were a more useful adjunct to cytology than FISH or karyotyping alone.