The difficulty of making a malignant mesothelioma diagnosis continues to stimulate discussion in the medical community. Last month, Dr. Aliya Husain from the Department of Pathology at the University of Chicago, and her colleague Qudsia Arif, published a short and direct article titled “Malignant Mesothelioma Diagnosis” in Archives of Pathology and Laboratory Medicine. The published context for the article states “mesothelioma is a relatively rare pleural tumor that may mimic benign mesothelial lesions and various other tumors . . . this makes the diagnosis challenging for the pathologist.” 

Below are three quick takeaways from the article:

1. Invasion of preexisting tissue, particularly fat, remains the key indicator of malignancy.

2. Calretinin, WT-1, CK 5/6, and D2-40 remain the most useful mesothelial markers, with MOC31, BG8, CEA, and BerEp4 the most useful carcinoma markers.  Sarcomatoid mesotheliomas and the sarcomatoid component of bi-phasic mesotheliomas “may lose immunoreactivity for most markers in a majority of cells; however, calretinin and D2-40 are more likely to remain immunoreactive.”  TTF-1 and napsinA are most useful in differentiating lung adenocarcinoma.

 [M]esothelioma is a relatively rare pleural tumor that may mimic benign mesothelial lesions and various other tumors . . . .

3. While p16 deletion is reported in the vast majority of epithelioid and sarcomatoid pleural mesotheliomas, immunohistochemistry is NOT recommended as a method for detecting p16 deletion.  Why?  According to the authors, immuno staining for the loss of p16 protein expression correlates with p16 deletion, but can also be negative without the deletion, or positive in a FISH-proven homozygous deletion.

The article can be found here.

See: Arif & Husain, “Malignant Mesothelioma Diagnosis,” Arch Pathol Lab Med, Vol 139, 978 – 980, August 2015.