Updates on grading mesothelioma

Mesothelioma: morphologic and immunohistochemical findings

This paper reviews some basic and some new concepts in the diagnosis of mesothelioma. The term "malignant mesothelioma" is no longer recommended; rather, any tumor labeled "mesothelioma" is presumed to be malignant. Clinical and radiologic information is very useful in the diagnosis of mesothelioma; in particular, nodular pleural thickening on CT is usually a marker of malignancy. The literature on markers that separate mesotheliomas from metastatic carcinomas has become very complex and frequently misleading, with many recommended markers actually demonstrating poor specificity. However, newer data show that a combination of HEG1 (clone SKM9-2) and claudin‑4 staining provides extremely high accuracy in separating epithelioid mesotheliomas from non-small-cell lung carcinomas with just two immunostains. This combination works at other sites as well, but caution should be used when high-grade serous carcinoma is in the differential, because all "mesothelioma" markers can also stain high-grade serous carcinomas. There are, unfortunately, no sensitive or specific markers for sarcomatoid mesotheliomas. A variety of immunohistochemical and fluorescence in situ hybridization (FISH) markers are useful in separating benign from malignant mesothelial proliferations; immunohistochemal staining for BAP1, MTAP (or CDKN2A FISH), and NF2/Merlin (or NF2 FISH) will enable the diagnosis of most mesotheliomas. Mesothelioma in situ is now recognized as either a single layer of bland cuboidal mesothelial cells that have lost BAP1, and sometimes MTAP, on immunohistochemical staining, or a process that is morphologically identical to a well-differentiated papillary mesothelial tumor that has lost BAP1/MTAP. Mesothelioma in situ probably always progresses to invasive mesothelioma, but this process is often quite slow.

Global burden of mesothelioma attributable to occupational asbestos exposure in 204 countries and territories: 1990-2019

Malignant mesothelioma, a rare and aggressive cancer primarily caused by occupational asbestos exposure, has a poor prognosis. This study leverages the Global Burden of Disease (GBD) 2019 dataset to analyze the burden of mesothelioma linked to occupational asbestos exposure from 1990 to 2019. The analysis includes the number of mesothelioma deaths and disability-adjusted life years (DALYs) attributable to occupational asbestos exposure, focusing on trends in age-standardized mortality rate (ASMR) and age-standardized disability-adjusted life-year rate (ASDR) by year, age, sex, country, region, and Socio-demographic Index (SDI). In 2019, 91.7% of mesothelioma deaths and 85.2% of DALYs were attributable to occupational asbestos exposure, resulting in 26,820 (95% UI 24,312-28,622) deaths and 569,429 (95% UI 509,956-617,484) DALYs. Despite a decline in ASMR and ASDR from 1990 to 2019, the absolute number of deaths and DALYs almost doubled. The United States reported the highest number of mesothelioma deaths, while China had the highest number of DALYs. Age-specific mortality rates and DALYs decreased in the 25-74 age group but increased in the 75+ age group. In conclusion, occupational asbestos exposure remains the primary cause of mesothelioma worldwide, with an increasing number of deaths and DALYs. The highest incidence rates are observed in high-income areas, and rates are rising in low-income areas. It is crucial to raise awareness about the hazards of asbestos to reduce the global burden of mesothelioma linked to occupational exposure.

Successful treatment of simultaneous malignant pleural mesothelioma and pulmonary adenocarcinoma: A case report

The present report described the case of a 74-year-old male patient with asbestos exposure whose chest computed tomography revealed a right lower lobe nodule and right pleural effusion. Pleural biopsy led to the diagnosis of epithelial malignant pleural mesothelioma (cT2N0M0, stage IB). Combination therapy with cisplatin + pemetrexed led to the complete remission of malignant pleural mesothelioma; however, the right lower lobe nodule grew in size over time. The patient was subsequently diagnosed with lung adenocarcinoma (cT1aN0M0, stage IA1) by computed tomography-guided biopsy performed 18 months after chemotherapy initiation and achieved remission of lung adenocarcinoma with stereotactic radiotherapy. The patient was alive without recurrence at the 12-month follow-up. The present case illustrated that multiple active regimens are currently available for malignant pleural mesothelioma and lung cancer that can aid in the treatment of complex cases.

Timely Surgical Resection Achieved Prolonged Remission in Patients With Malignant Mesothelioma of the Tunica Vaginalis Testis and Retroperitoneal Recurrence

Malignant mesothelioma of the tunica vaginalis testis (MMTVT) is a rare tumor of the testicular sheath. More than 50% of cases initially present as recurrent hydrocele, but there have also been documented cases with hematocele, inguinal hernia, or epididymitis. Due to the non-specific symptoms and signs of the disease, it is almost always diagnosed intra- or postoperatively. The lack of standardized therapy protocols, as well as the lack of evidence supporting systemic chemotherapy, have fueled arguments in favor of the necessity of retroperitoneal lymph node dissection (RPLND) in the treatment of the disease, especially in the case of lymph node metastasis. We present a case of MMTVT achieving prolonged remission after timely and extensive surgical treatment.