Protein staining tests are a useful tool in diagnosing sarcomatoid mesothelioma — the most aggressive mesothelioma cell type — but aren’t reliable enough on their own, according to new research.

A May 3 report in the International Journal of Surgical Pathology concluded that staining tests — which involve dyeing tissue samples to highlight or isolate proteins associated with certain cancers — work best when paired with clinical findings and radiology reports.

Researchers from the University of Texas’ M.D. Anderson Cancer Center compared the results of 64 patients diagnosed with sarcomatoid pleural mesothelioma, the least common type of mesothelioma cell. The 51 men and 13 women ranged in age from 42 to 79 years old.

Testing Parameters

All of the patients received diagnostic imaging of their lungs, underwent surgical resection via extrapleural pneumonectomy — the removal of a lung — and received immunohistochemical testing of various protein levels.

“Even though the use of immunohistochemical stains plays an important role in the final interpretation, the best results are accomplished by a global interpretation of clinical, radiographical, and immunohistochemical findings.”

Testing started off strong, with chemical staining positively identifying the protein cytokeratin AE1/AE3 — which is associated with epithelial cancers like mesothelioma — in all patients.

However, the results were decidedly more mixed for other protein markers typically associated with pleural mesothelioma, such as keratin 5/6.

Mixed Results

The two most common positive markers for sarcomatoid mesothelioma cells — D2-40 and calretinin — were likewise “seen in different proportions,” the researchers wrote. Ironically, several protein markers that often can’t identify sarcomatoid mesothelioma cells — such as WT1 — showed positive results in a few cases.

Lastly, all patient tumor samples tested negative for carcinomatous epitopes, the team reported.

Based on these results, the researchers concluded that there “does not seem to be a single immunohistochemical stain” that can positively identify sarcomatoid mesothelioma cells.

‘Global Interpretation’ Is Key

“Our findings show that even though the use of immunohistochemical stains plays an important role in the final interpretation, the best results are accomplished by a global interpretation of clinical, radiographical, and immunohistochemical findings,” the team concluded.

Immunohistochemical staining has an iffy track record in mesothelioma research. Back in March, Canadian researchers concluded that staining tests for a key protein weren’t able to properly distinguish between benign and malignant mesothelioma cells.

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