[1780] Patterns of Metastases to N2 Lymph Nodes from Biphasic Pleural Malignant Mesothelioma.

Maria G McIntire, William G Richards, David J Sugarbaker, Lucian R Chirieac. Caris Life Sciences, Newton, MA; Brigham and Women's Hospital, Boston, MA

Background: Pathologic classification of diffuse malignant mesothelioma (DMM) into epithelioid, sarcomatoid, and biphasic types, according to the current WHO criteria, is an important predictor of survival. Studies have shown that patients with extrapleural lymph node metastases have a poor prognosis following surgery. However, there are no studies of biphasic DMM examining which component is more likely to spread to N2 lymph nodes. The goal of this study was to characterize the histology of metastases to N2 lymph nodes from patients with biphasic DMM.
Design: We identified 715 consecutive patients with MM (462 epithelioid, 231 biphasic, and 22 sarcomatoid types) treated by extrapleural pneumonectomy (EPP) at Brigham and Women's Hospital between 1988 and 2009. Of the 231 biphasic MMs, we found 74 patients who also had sampling of mediastinal lymph nodes with a diagnosis of DMM metastatic to those lymph nodes. We evaluated 65 of these patients with biphasic DMM, N2 lymph node metastases, and available pathology material for the presence of epithelioid, sarcomatoid or both histologies in the positive N2 lymph nodes.
Results: All 65 patients (11 F/54 M; mean age 60.1; range 31-88) had a diagnosis of biphasic DMM metastatic to N2 lymph nodes. Thirty eight patients (58%) with biphasic DMM had both epithelioid and sarcomatoid components in the N2 lymph nodes and 27 (42%) showed spread only of the epithelioid component to the N2 lymph nodes. There were no biphasic DMMs that had N2 spread of the sarcomatoid component alone. A mixed histology in the lymph nodes is highly specific of a biphasic DMM (specificity=100%), whereas an epithelioid histology in N2 lymph nodes indicates that the primary tumor may be either an epithelioid or a biphasic DMM (sensitivity=70.4%).
Conclusions: Our data suggest that a diagnosis of mixed DMM in patients with N2 lymph node metastases is highly predictive of biphasic DMM in the primary tumor (p<0.0001, Fisher exact test). However, the finding of an epithelioid component alone in the mediastinal lymph nodes does not preclude from a diagnosis of biphasic DMM in the EPP specimen. The results of our study emphasize the importance of histologic classification and highlight the biologic complexity of tumor morphogenesis and progression in biphasic DMM.
Category: Pulmonary

Tuesday, March 1, 2011 9:30 AM

Poster Session III # 278, Tuesday Morning


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