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S. Prabhakaran
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P1.09 - Mesothelioma (ID 695)
- Event: WCLC 2017
- Type: Poster Session with Presenters Present
- Track: Mesothelioma
- Presentations: 1
- Moderators:
- Coordinates: 10/16/2017, 09:30 - 16:00, Exhibit Hall (Hall B + C)
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P1.09-003 - Malignant Mesothelioma Versus Synovial Sarcoma: An Analysis of 19 Cases with Molecular Diagnosis (ID 9390)
09:30 - 09:30 | Author(s): S. Prabhakaran
- Abstract
Background:
Intrathoracic synovial sarcomas (SSas) are well documented in the literature and characterized by a distinctive t(X;18) translocation. The histologic appearances of a monophasic or biphasic SSa can lead to confusion with biphasic or sarcomatoid mesothelioma (MM). The distinction of pleural SSa from pleural MM is important, because SSas may be responsive to ifosfamide-based chemotherapy and have no proven causal relationship to prior asbestos exposure. Demonstration of the t(X;18) by cytogenetics, fluorescence in situ hybridization (FISH) or reverse-transcriptase polymerase chain reaction is the gold standard for diagnosis, but availability of molecular diagnosis can be limited and testing is time consuming. Recently, it has been suggested that immunohistochemistry (IHC) for transducin-like enhancer of split 1 (TLE) is reliable for diagnosis of SSa and may replace molecular diagnosis.
Method:
We reviewed 19 pleura-based malignancies that had either been referred for a potential diagnosis of SSa, or where SSa was a differential diagnosis considered by the authors, based on morphology. Only cases with molecular diagnostics and clinical follow-up and blocks or unstained slides for further IHC studies are included.
Result:
Fourteen (14/19) cases were diagnosed as MM with morphology indistinguishable from SSa, based on lack of the t(X;18) by FISH and/or PCR, whereas 5 cases were diagnosed as SSa based on molecular diagnostics in conjunction with morphology. The mean age at diagnosis was 40.6 and 70.35 years for SSa and MM respectively. In the MM group, 21% of the patients were female, compared to 80% in the SSa group. Median survival after diagnosis was 9 months for MM, whereas all of the SSa patients were alive after follow-ups ranging from 3 months to 21 years. On average, MMs were larger tumours (average size of 97 mm, ranging from 20 to 220 mm), compared to 37 mm (range 20-50 mm) in SSa. Pleural plaques were present in 9 of the MM patients, with no information on plaques for 4 patients, and with 1 patient not having plaques, whereas only one of the SSa patients was confirmed as having pleural plaques. Of note, 7 of the MMs showed positive labelling for TLE1, with 7 MM not showing labelling, whereas all 5 SSas showed positive labelling.
Conclusion:
This indicates that positive labeling for TLE1 in isolation is insufficient for discrimination between MM vs SSa in pleura-based lesions with SSa-like morphology, and that molecular studies remain the gold standard for diagnosis.
