[1792] High Prevalence of Atypical Mesothelial Proliferation in Extrapleural Pneumonectomy Specimens; Further Evidence of a Potential Precursor Lesion to Invasive Mesothelioma?

LA Doyle, JM Corson, DJ Sugarbaker, LR Chirieac. Brigham and Women's Hospital, Boston, MA

Background: Atypical mesothelial proliferation (AMP) is thought to represent a potential precursor lesion to invasive pleural mesothelioma. To our knowledge there is no published literature describing the clinicopathologic characteristics of AMP. The aim of this study was to evaluate the prevalence of AMP in extrapleural pneumonectomy (EPP) specimens for invasive mesothelioma and to correlate AMP with clinicopathologic features.
Design: We studied 46 consecutive EPPs with available surgical material (mean 22 slides per case, range 12-30), performed at a single institution for invasive mesothelioma (IM) over a period of 16 months. Each case was assessed independently by two pathologists for the presence or absence of AMP according to currently established morphologic criteria. We evaluated architectural and cytologic features, the prevalence and extent of AMP and correlated clinicopathologic features between mesotheliomas with and without AMP.
Results: All 46 EPPs showed invasive mesothelioma (n=30 epithelioid, n=15 mixed and n=1 sarcomatoid). There were 40 men (87%) and 6 women (13%), with an average age of 62.9 years (range 38-79). AMP was identified in 10 (22%) EPP specimens, in a mean of 3.5 slides (range 1-6). Nine cases (90%) were associated with epithelioid mesothelioma and 1 case (10%) with mixed mesothelioma. Common architectural patterns of AMP were a single cell layer proliferation (n=8), stratified proliferations (n=5) and papillary proliferations (n=5). Six cases (60%) had mixed AMP growth patterns. In AMP with a single cell layer proliferation, prominent nucleoli were present in at least 50% of lesional cells. AMP was present in EPPs with lower weights (median 747g vs. 1110g, p=0.03) and in older patients (68 vs. 63 years, p=0.02, 95% CI -15.38 to -1.586).
Conclusions: In our study we show that the prevalence of AMP in EPPs is higher than anticipated at 22%, and is more frequent in older patients and in specimens with lower weights. Further studies are needed to investigate the clinical significance of AMP and the role of AMP in the pathogenesis of mesothelioma.
Category: Pulmonary

Tuesday, March 23, 2010 1:00 PM

Poster Session IV # 246, Tuesday Afternoon


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