Malignant mesothelioma: A clinicopathological study of 76 cases with emphasis on immunohistochemical evaluation along with review of the literature

Abstract

Introduction: Malignant mesothelioma is an aggressive neoplasm arising from serosal lining and has a poor prognosis. Definite diagnosis requires confirmation through a biopsy; however, it is sometimes difficult on microscopic evaluation alone and requires the use of a wide panel of immunohistochemical markers. So, immunohistochemistry (IHC) is of paramount importance and must be routinely used for a definite diagnosis. Till date, very few studies on morphology and detailed IHC markers of mesothelioma have been reported from India.

Aims: To analyze the histomorphological findings of malignant mesothelioma, study the utility and role of the various immunohistochemical markers.

Material and methods: A total of 76 cases of mesotheliomas diagnosed at a tertiary cancer center in Udaipur were analyzed retrospectively from January 2015 to January 2020. Comprehensive data were analyzed including demographic, clinical, radiological, histopathological features along with a wide panel of IHC markers.

Results: Mesothelioma occurs over a wide age range from 40 to 70 years. It most commonly involved pleura in 68 cases (89.47%) with very few cases from the peritoneum. On computed tomography (CT) scan, nodular pleural or peritoneal thickening was present. On microscopy, the most common histopathological type was epithelioid mesothelioma (58 cases, 74.3%) followed by sarcomatous (9 cases, 12.8%), deciduoid (6 cases, 8.6%), and 3 cases of biphasic (4.3%). On IHC, WT1, mesothelin, and calretinin markers were positive in 85.91%, 80%, and 93.33% cases of mesothelioma, respectively. Other markers were helpful to rule out differential diagnosis in difficult scenarios.

Conclusion: Therefore, the correlation of histopathology with clinico-radiological findings and judicious use of a panel of IHC markers is required for routine evaluation and definite diagnosis. IHC is also useful in situations with similar morphological spectrum in specific locations.

Keywords: Differential diagnosis; IHC markers; epithelioid type; histomorphological evaluation; mesothelioma; pleural involvement.