New Tips for Diagnosing Malignant Peritoneal Mesothelioma

Malignant peritoneal mesothelioma is an aggressive cancer that often mimics other conditions. This can make it difficult to get a definitive diagnosis. But a new report in Pathology Case Reviews provides tips for identifying peritoneal mesothelioma.

Diagnosing Malignant Peritoneal Mesothelioma

Mesothelioma is usually diagnosed after a person experiencing symptoms goes to a doctor. Patients often complain of vague abdominal symptoms, such as pain, nausea, bloating, weight loss. Distinguishing peritoneal mesothelioma from other cancers is important to ensure appropriate treatment.

One thing a doctor may do is perform a tissue biopsy. The doctor will remove a part of the tissue (suspected mesothelioma) for examination. A biopsy is the “gold standard” and the single most important procedure for an accurate diagnosis.

Doctors identify mesothelioma using diagnostic tissue biomarkers. This is called immunohistochemistry.

Biopsies and Immunohistochemical Stains

All biopsy and fluid samples are sent to a pathologist. Pathologists use microscopes and special stains and assays to find out if the tissue contains mesothelioma.

But under the microscope, mesothelioma may look like other types of cancer which is a challenge. Because of this, special tests and assays are used by pathologists. These tests use special stains called immunohistochemistry. They look for tell-tale proteins (antigens) often found in mesothelioma cells.

But many of the common immunohistochemical stains lack specificity. This makes it difficult to narrow the diagnosis down further. This means that a second test is then required to categorize the peritoneal mesothelioma diagnosis.

Dr. Kristen Stashek from the University of Maryland noted that “Malignant peritoneal mesothelioma is an aggressive malignancy that often mimics carcinomatosis both clinically and histologically, making definitive diagnosis challenging for the general pathologist.”

Dr. Stashek’s team of pathologists from the University of Maryland recently published a list of common pitfalls when it comes to diagnosing peritoneal mesothelioma.

Pathology Examination is Key for Diagnosis

Many mesothelioma patients have a misdiagnosis or a delay in diagnosis.

A tissue biopsy is an important step in being diagnosed correctly. A biopsy can help doctors determine the cell type of the disease. This is important information that can be used to create an effective treatment plan.

Pathologists must select the best test to categorize the mesothelioma diagnosis. To do this, they must have an understanding of the markers.

Some markers are helpful in distinguishing different malignant mesothelial tumors. Whereas others are more useful in distinguishing mesothelioma from other cancers. Some of the more widely available mesothelial markers include a protein called calretinin. Newer markers used to diagnose mesothelioma include BAP1 and MTAP.

The diagnostic utility of these markers is particularly useful. It allows for the distinction between mesothelioma and pulmonary adenocarcinoma tumors.

Sources

Stashek, Kristen M., Rachel Fanaroff, and Allen P. Burke. “Immunohistochemical Pitfalls in Malignant Peritoneal Mesothelioma: A Case Report and Review for the General Pathologist.” AJSP: Reviews & Reports 27, no. 3 (2022): 94-97. https://journals.lww.com/pathologycasereviews/Fulltext/2022/05000/Immunohistochemical_Pitfalls_in_Malignant.3.aspx