Reliable Mesothelioma Diagnosis May Be Possible Without a Biopsy

In the future, you might not need to undergo a biopsy to reliably reveal whether you have mesothelioma.

Your doctor may instead be able to reliably diagnose you by looking at BAP1 immunohistochemistry and p16 FISH analysis of your chest fluids, according to researchers at the University of Washington in Seattle. This intriguing possibility was reported in the American Journal of Surgical Pathology.

According to the researchers, BAP1 loss and p16 deletion in effusion cytology specimens appear to be a reasonably sure indicator of mesothelial malignancy.

The two biomarkers are particularly useful if the mesothelial proliferation is well sampled, although BAP1 tends to be easier to interpret when the sample being worked with is insubstantial.

Mesothelioma Diagnosis Biomarker Debate

The article is titled “Utility of BAP1 Immunohistochemistry and p16 (CDKN2A) FISH in the Diagnosis of Malignant Mesothelioma in Effusion Cytology Specimens.” FISH stands for fluorescence in situ hybridization.

The authors start out by acknowledging that making a diagnosis of malignant mesothelioma from a sampling of effusion cytology specimens is currently the subject of much debate among scientists.
The researchers note, however, that BAP1 immunohistochemistry and p16 FISH have recently been reported as reliable markers of malignancy in biopsies of mesothelioma.

Consequently, the researchers decided to proceed with an investigation into the value of using these two biomarkers in conjunction with effusion cytology specimen sampling.

The researchers structured their study so that they could answer the question of whether effusion cytology specimen sampling could be as reliable as making a diagnosis from a biopsy.

Biopsy is the current gold standard for making an accurate mesothelioma diagnosis. But it’s an invasive procedure, while effusion cytology sampling is less so.

To get their answer, the researchers obtained 15 biopsies of epithelial mesotheliomas along with three benign mesothelial reactions.

Accompanying all were corresponding effusion cytology paraffin-embedded cell blocks. It turned out that four of the effusion cytology specimens were not substantial enough to permit a p16 FISH analysis.

However, the good news was that those four were more than adequate to conduct a BAP1 immunohistochemistry analysis.

Comparing Malignant Mesothelioma with Benign

When all was said and done, the researchers observed that each of the remaining 11 cell blocks exhibited either a loss of BAP1 or a deletion of p16. In some case, it was both BAP1 loss and p16 deletion.

The incidence of BAP1 loss all by itself was seen in 67 percent of the biopsies. In the cytology specimens, the BAP1 loss was identical — 67 percent.

The incidence of p16 deletion all by itself was seen in 80 percent of the biopsies. In the cytology specimens, the p16 deletion was determined to have occurred in 73 percent of them.

Loss of BAP1 and p16 deletion occurring together was detected in 47 percent of the biopsies and in 42 percent of the cytology specimens.

In other words, the loss of BAP1 and the deletion of P16 were essentially the same for both the biopsy and cytology specimens, the researchers wrote.

The researchers also noted that among the specimens in their study were two from patients with the peritoneal form of mesothelioma. The researchers said these two specimens exhibited BAP1 loss but not p16 deletion.

For any of the researchers’ discoveries to be useful to mesothelioma diagnosis, they had to also evaluate a cohort of benign mesothelial reactions and corresponding cytology specimens.

In examining the benign specimens, the researchers found none of them exhibited any loss of BAP1 or deletion of p16.

Translation: if there is no BAP1 loss or p16 deletion, then it is likely there is no malignancy.