Human Pathology 2020 September 2 [Link]
Sarita Prabhakaran, Ashleigh Hocking, Chankyung Kim, Matthew Hussey, Sonja Klebe
Malignant pleural mesothelioma is associated with asbestos exposure and poor outcomes. The usefulness of immunohistochemistry for diagnosis of sarcomatoid mesothelioma, especially the desmoplastic type, is limited, and more effective markers are required. GATA binding protein 3 (GATA3) has been suggested as a diagnostic marker for sarcomatoid mesothelioma. The potential usefulness of GATA3 for prognostication and its clinical and pathological correlations in different subtypes of mesothelioma have not been evaluated. We investigated the immunohistochemical labeling and associations for GATA3, BRCA1-associated protein 1 (BAP1), and Ki67 labeling in three major histological types of pleural malignant mesotheliomas. We examined 149 clinically annotated malignant mesotheliomas and assessed associations of GATA3 expression with clinical variables and prognosis. In addition, we labeled 10 cases of fibrous pleuritis with GATA3, all of which were negative. GATA3 was positive in 75 of 149 (50%) mesotheliomas, with the highest incidence of labeling seen in the sarcomatoid subtype (73%), compared with the biphasic (50%) and epithelioid (40%), mesotheliomas. A total of eight desmoplastic mesotheliomas showed labeling with GATA3. Patients whose tumors had sarcomatoid histology showed poorer survival than those with the other subtypes (p < 0.001), but overall GATA3 labeling did not have a statistically significant association with survival (p = 0.602). There was no association of GATA3 labeling and BAP1 status or Ki67 index. Our study includes the largest cohort of mesotheliomas that has been labeled for GATA3 to date. GATA3 is a useful marker for sarcomatoid mesothelioma, including the desmoplastic subtype. Discordance in GATA3 and BAP1 labeling of epithelioid and sarcomatoid components in the biphasic subtype is not uncommon.