Tumor Grade and Peritoneal Mesothelioma Survival

The size, shape and extent of a peritoneal mesothelioma tumor are not the only characteristics that impact mesothelioma survival.

A team of pathology researchers from three top US cancer centers say nuclear features – how the nuclei of the cancer cells look and behave –  may also play a significant role in mesothelioma outcomes.

Their new study, published in the American Journal of Surgical Pathology, highlights the importance of pathological evaluation of peritoneal mesothelioma cells in determining a patient’s prognosis.

Grading Mesothelioma Tumors

Peritoneal mesothelioma, which occurs in the abdomen, is a rare form of a rare cancer, accounting for about a fifth of the 2,500 cases of mesothelioma diagnosed in the US each year. Most of the remaining cases are lung-related pleural mesothelioma.

Although nuclear grading, the process of assigning a “grade” to a tumor based on the characteristics seen in the nucleus of its cells, has been shown to correlate with pleural mesothelioma prognosis, the current study is the first to examine the impact of tumor grade on peritoneal mesothelioma survival.

Understanding Tumor Grading

According to the National Cancer Institute, tumor grade is “the description of a tumor based on how abnormal the tumor cells and the tumor tissue look under a microscope.”

Mesothelioma cells that look very abnormal compared to healthy cells are ranked higher on the 1 to 4 cancer grading scale. In general, malignancies with a Grade of 1 or 2 tend to grow and spread slowly while those assigned a Grade of 3 or 4 tumors tend to grow faster and spread more quickly.

Tumor grade is different from mesothelioma tumor stage, which refers to the size or reach of the primary tumor and the level of cancer metastasis. Grading can only be done by looking at cells under a microscope.

Tumor Grade and Mesothelioma Survival

The current study of the relationship between tumor grade and peritoneal mesothelioma prognosis focused of the cases of 46 mesothelioma patients with the epithelioid subtype (the most common subtype).

The cases were divided into two tiers based on their tumor grade and their level of mitoses or symmetrical division of the cell nucleus during proliferation. The team reports that cases in the lower-tier, which corresponded to the lowest tumor grades, were most likely to experience long-term mesothelioma survival.

According to study author Kari Valente, MD, with Wake Forest Baptist Health in North Carolina, “The low-grade tier had higher overall survival with a median of 11.9 years and 57% at 5 years when compared with the high-grade tier with a median of 3.3 years and 21% at 5 years (P=0.002).”

These results are similar to what scientists at Memorial Sloan Kettering Cancer Center in New York found to be true of pleural mesothelioma in 2011. That study called nuclear grading a “simple, practical, and cost-effective prognostic tool” for predicting clinical outcomes and recurrence in pleural mesothelioma.

Sources:

Valente, K, et al, “A Histomorphologic Grading System That Predicts Overall Survival in Diffuse Malignant Peritoneal Mesothelioma With Epithelioid Subtype”, July 19, 2016, American Journal of Surgical Pathology, Epub ahead of print

Kyuichi, K, et al, “A nuclear grading system is a strong predictor of survival in epithelioid diffuse mailgnant pleural meosthelioma”, February 2012, Modern Pathology, pp. 260-271