Malignant mesothelioma following thoracic radiotherapy for lung cancer

When the Diagnosis of Mesothelioma Challenges Textbooks and Guidelines

The diagnosis of malignant mesothelioma (MPM) does not pose difficulties when presenting with usual clinico-radiologic features and morphology. Pathology textbooks and national/international guidelines generally describe the findings of classic MPM, underlining common clinical presentation, the gold standard of sampling techniques, usual morphologic variants, immunohistochemical results of several positive and negative primary antibodies in the differential diagnosis, and the role of novel molecular markers. Nevertheless, MPM often does not follow the golden rules in routine practice, while the literature generally does not sufficiently emphasize unusual features of its manifestation. This gap may potentially create problems for patients in sustaining a difficult diagnosis of MPM in clinical practice and during legal disputes. Indeed, the guidelines accidentally tend to favor the job of lawyers and pathologists defending asbestos-producing industries against patients suffering from MPM characterized by uncommon features. The current review is aimed at underlining the wide spectrum of clinical and radiological presentation of MPM, the possibility to consistently use cytology for diagnostic intent, the aberrant immunohistochemical expression using so-called specific negative and positive primary antibodies, and finally proposing some alternative and more unbiased approaches to the diagnosis of MPM.

The Association between Malignant Pleural Mesothelioma and Thoracic Radiation Therapy for Hodgkin's Lymphoma: The First Case Report in Japan

Malignant pleural mesothelioma (MPM) is mostly observed in patients with a history of asbestos exposure. Although other causes are rare, there are several reports of MPM induced by therapeutic radiation, mainly in Europe and North America. However, no such case has been reported in Japan. We herein report a 50-year-old Japanese woman who developed MPM 25 years after thoracic radiation therapy for Hodgkin's lymphoma. The patient had no history of exposure to asbestos; therefore, her history of radiation therapy was considered to be the cause of MPM. Clinicians should consider secondary MPM in patients with a history of thoracic radiation therapy.

Post-irradiation pericardial malignant mesothelioma with deletion of p16: a case report

Malignant mesotheliomas are rather uncommon neoplasms associated primarily with asbestos exposure; however, they may also arise as second primary malignancies after radiation therapy, with a latency period of 15-25 years. Numerous studies have reported an association between pleural malignant mesothelioma and chest radiation performed for other malignancies; on the other hand, post-irradiation mesotheliomas of the pericardium have been reported in only a few published cases to date, and no homozygous deletion of 9p21 has been described in such cases. We report the case of a 48-year-old man with a history of Hodgkin's lymphoma and no prior asbestos exposure who developed pericardial malignant epithelioid mesothelioma. We further discuss the cytologic, histologic, immunophenotypic, and fluorescence in situ hybridization findings in this case. To our knowledge, this is the first well-documented case of post-radiation pericardial malignant mesothelioma showing homozygous deletion of 9p21. Homozygous deletion of 9p21, the locus harboring the p16 gene, is present in post-irradiation pericardial malignant mesothelioma.

Novel systemic therapy against malignant pleural mesothelioma

Malignant pleural mesothelioma is an aggressive tumor of the pleura with an overall poor prognosis. Even with surgical resection, for which only a subset of patients are eligible, long term disease free survival is rare. Standard first-line systemic treatment consists of a platinum analog, an anti-metabolite, and sometimes anti-angiogenic therapy, but there is currently no well-established standard therapy for refractory or relapsed disease. This review focuses on efforts to develop improved systemic therapy for the treatment of malignant pleural mesothelioma (MPM) including cytotoxic systemic therapy, a variety of tyrosine kinase inhibitors and their downstream effector pathways, pharmacologic targeting of the epigenome, novel approaches to target proteins expressed on mesothelioma cells (such as mesothelin), arginine depletion therapy, and the emerging role of immunotherapy. Overall, these studies demonstrate the challenges of improving systemic therapy for MPM and highlight the need to develop therapeutic strategies to control this disease.

Mesothelioma not associated with asbestos exposure

CONTEXT

Despite asbestos being identified as the single most important cause of malignant mesothelioma, the tumor is known to occur in only 10% to 20% of heavily exposed individuals. In addition, about 20% of the patients have no history of asbestos exposure even after detailed assessment. Therefore, there has been speculation for some time that asbestos alone may not be sufficient to cause mesothelioma and that other factors may be involved either as cocarcinogens or as independent mechanisms of cancer causation.

OBJECTIVE

To give a brief review of nonasbestos fiber erionite and therapeutic radiation as 2 established examples of asbestos-independent mechanisms, of the potential emerging role of man-made fibers such as carbon nanotubes, and of polyoma virus SV40 (simian virus 40) as a potential example of the cocarcinogenic mode of involvement.

DATA SOURCES

Relevant recent literature has been surveyed to portray and provide the evidence in favor of the examples.

CONCLUSIONS

Erionite has emerged as the most important example of nonasbestos-mediated cause of mesothelioma in regions such as Turkey where exposure to this type of fiber is highly prevalent. Recently, the polyoma virus SV40 has been unexpectedly discovered as an effective cocarcinogen of asbestos in the causation of animal mesothelioma, though despite considerable research, its potential role in human mesothelioma remains unproven.

Risk of second tumor in intracranial germinoma patients treated with radiation therapy: the Johns Hopkins experience

BACKGROUND

We reviewed the risk of second tumor (ST), both malignant and benign, in germinoma survivors followed at the Johns Hopkins Hospital (JHH).

METHODS

Between 1977 and 2002, 27 patients with intracranial germinoma were treated with radiation therapy (RT). In the presence of competing events, a cumulative incidence function of ST was estimated using the minimal time interval from the date of diagnosis to the date of ST, date of death, or date of last follow-up.

RESULTS

Five patients (18%) developed a ST of which 4 (15%) were malignant. One developed a benign falcine meningioma. The cumulative incidence of ST was 9% at 11 years (95% CI, 0-22%).

CONCLUSIONS

The relative contributions of RT and patient susceptibility to a ST cannot be determined but suggests the need for long-term surveillance, including testicular self-exams in male germinoma survivors. Current trials of chemotherapy and reduced RT dose and volume offer the prospect of a lower risk of treatment-induced ST.