Mesothelioma is an aggressive malignancy that primarily attacks the pleural surfaces surrounding the lungs, although it can also attack the peritoneum and—in rare cases—the pericardium and the mesothelial tissue surrounding the male reproductive system. Its normal behavior pattern is characterized by a diffuse spread of malignant cells throughout an entire surface area, where the boundaries between cancerous and non-cancerous tissues are blurred and often break down—making surgical resection of the cancer extremely difficult, if not impossible. This pattern is in marked contrast to other forms of cancer that present as locally-invasive, individually-identifiable tumors that evidence a clear boundary between the tumor and the otherwise healthy surrounding tissue.

Within the last decade, however, articles describing a number of cases that depart from this behavior pattern have appeared in the literature. These articles describe cases of histologically-proven pleural mesothelioma where individuals presented with locally-invasive pleural tumors that did not show any sign of diffuse spread and were more amenable to surgical resection than is the standard form of pleural mesothelioma. While these findings show a clear need for more research, its extreme rarity has limited researchers’ abilities to learn more about it. There are less than 100 proven cases of what is now known as localized malignant pleural mesothelioma in the literature, so large-scale studies of this subclass are currently impossible. Our knowledge of the disorder is anecdotal at best and is entirely based on journal descriptions of individual cases and presentations. Researchers from the United Kingdom have recently added to the literature on localized malignant pleural mesothelioma with an article that describes their experience with ten cases over an eight-year period.

What follows is a summary of their article.

Overview of the Study

The authors of the study work in the Department of Thoracic Surgery at Glenfield Hospital in Leicester, UK. During an eight-year period they performed surgery for 218 patients with pleural mesothelioma—10 of whom presented with the localized subtype under discussion here. These ten patients were all males and the median age at presentation was almost 66 years old. All had pathologically-confirmed malignant pleural mesothelioma. In terms of the histological subtypes of their diagnoses: four of the patients presented with epitheloid mesothelioma, four with sarcomatoid mesothelioma and two with the bi-phasic subtype. They all underwent surgery to remove a locally-invasive tumor that had infiltrated at least the chest wall: six presented with right-side infiltration and four with left-side infiltration. All patients underwent some form of pleurectomy: seven patients received a subtotal parietal pleurectomy, while the other three received a total parietal pleurectomy.

The results of the surgery were statistically much better than the results obtained after surgery for standard-form pleural mesothelioma. There were no deaths within 30 days of the surgery, although two needed drainage for post-surgery pleural effusions. The authors report microscopically complete resection in two patients and macroscopically complete resection in the remaining eight. Two patients died within one year of surgery (one at three months and one at ten months) and two more showed progression of the disease, but they were still alive during the period of the study. The authors report median survival at 56 months, which is much longer than the median survival range of 8–16 months typically reported for standard pleural mesothelioma. They also note that the longest survivor in their cohort was still alive at 70 months post surgery—a very rare occurrence for mesothelioma patients.

Conclusion

The authors concur with the previously published literature that localized malignant pleural mesothelioma has a distinctly different behavior pattern than does the standard-form disease. Using locally aggressive surgery, they were able to achieve some form of complete resection in all ten patients and their median survival figure of 56 months is quite a bit longer than anything reported in the literature on standard-form pleural mesothelioma. However, they are quick to note that a sample size of only ten cases isn’t nearly large enough to draw any definitive conclusions from and they call, as do most doctors who’ve had any experience with this rare malignancy, for more research into its biology and overall behavior.

Labels: mesothelioma