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Background: We have recently proposed to reclassify the pleomorphic subtype of epithelioid malignant pleural mesothelioma (MPM) as nonepithelioid (biphasic/sarcomatoid) histology because of its similarly poor prognosis. We sought to investigate whether preoperative maximum standardized uptake value (SUVmax) on F-fluorodeoxyglucose (FDG) positron emission tomography (PET) correlates with histologic subtype in MPM., Methods: Clinical data were collected for 78 patients with MPM who underwent preoperative FDG-PET. We retrospectively classified the epithelioid tumors into five subtypes: trabecular, tubulopapillary, micropapillary, solid, and pleomorphic. Tumors were categorized by SUVmax into two groups: low (<10.0) and high (≥10.0)., Results: The median overall survival of epithelioid tumors with high SUVmax (n = 12) was significantly shorter (7.1 months) than that of epithelioid tumors with low SUVmax (n = 54, 18.9 months, p < 0.001) and comparable to nonepithelioid tumors (n = 12, 7.2 months). Epithelioid tumors with pleomorphic subtype (n = 9) had marginally higher SUVmax (mean ± SD: 10.6 ± 5.9) than epithelioid nonpleomorphic subtype (n = 57, 6.5 ± 3.2, p = 0.050), and were comparable to that of nonepithelioid tumors (n = 12, 9.1 ± 4.8). Among the epithelioid tumors with high SUVmax (n = 12), 50% (n = 6) showed pleomorphic subtype. In contrast, among epithelioid tumors with low SUVmax (n = 54), 6% (n = 3) showed epithelioid pleomorphic subtypes (p = 0.001). A positive correlation between mitotic count and SUVmax was observed (r = 0.30, p = 0.010)., Conclusions: Pleomorphic subtype of epithelioid MPM showed higher SUVmax than the epithelioid nonpleomorphic subtype and was similar to nonepithelioid histology. Preoperative SUVmax on FDG-PET in epithelioid MPM can indicate patients with pleomorphic subtype with poor prognosis, supporting their reclassification as nonepithelioid.

Malignant pleural disease (MPD) results in an estimated 150,000 cases of malignant pleural effusions (MPE) annually. The most common malignancies associated with MPD are primary malignant pleural mesothelioma (MPM) and metastatic lung cancer, breast cancer, and lymphoma. MPM is a rare, regionally aggressive malignancy whose incidence is increasing secondarily to the latency of disease progression. MPD is characteristic of advanced-stage pleural disease and portends a grave clinical prognosis with a median survival between 3 and 12 months. Preclinical investigations conducted in flank and intraperitoneal tumor models do not fully recapitulate the pleural tumor microenvironment, and the results are not directly translatable to the clinical setting. The protocol described herein provides a mouse model of MPM and MPD from nonhematogenous tumors, resulting in reproducible tumor location, tumor progression, animal survival, and histopathology. Pleural tumor growth in this model resembles the regionally aggressive clinical course and tumor microenvironment of human pleural cancers and provides an optimal animal model to investigate MPD biology and therapies.