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Mai Nishina



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    P23 - Mesothelioma, Thymoma and Other Thoracic Malignancies - Esophageal Cancer and Rare Tumors (ID 137)

    • Event: WCLC 2020
    • Type: Posters
    • Track: Mesothelioma, Thymoma and Other Thoracic Malignancies
    • Presentations: 1
    • Moderators:
    • Coordinates: 1/28/2021, 00:00 - 00:00, ePoster Hall
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      P23.04 - Primary Pulmonary Myxoid Sarcoma with EWSR1 Rearrangement: A Case Report (ID 2148)

      00:00 - 00:00  |  Presenting Author(s): Mai Nishina

      • Abstract
      • Slides

      Introduction

      Primary pulmonary sarcomas are extremely rare and comprise a heterogeneous group of sarcomas. Among them, primary pulmonary myxoid sarcoma (PPMS) is the rarest. Genetically, PPMS harbors an EWSR1-CREB1 fusion gene. This criterion was included in the latest WHO classification. To date, only 26 cases of PPMS have been reported in the English literature. Detection of EWSR1-CREB1 fusion by fluorescence in situ hybridization (FISH) or reverse transcription-polymerase chain reaction (RT-PCR) serves as a diagnostic clue; however, characteristic histological findings such as spindle or satellite cell proliferation accompanied by myxoid stroma are indispensable for the diagnosis of PPMS.

      Methods

      A 44-year-old male patient was referred to our hospital because an abnormal shadow was detected following chest radiography during a medical check-up. No abnormalities were detected upon physical and laboratory examinations.

      Results

      Chest computed tomography revealed a well-circumscribed solid mass 2.1 cm in diameter adjacent to the superior bronchus of the left lower lobe (B6). Bronchoscopic examination revealed an occlusion of the B6 by the tumor; however, a specific diagnosis was not achieved following transbronchial biopsy. The patient underwent segmentectomy for the complete resection of the tumor and for diagnostic purposes. Macroscopically, the tumor was a solitary mass measuring 2.3 cm × 1.5 cm in size with a gelatinous cut surface, and showed extraaxial intraparenchimal growth. Histopathological examination revealed multinodular and chicken-foot-like proliferation of spindle cells in a background of myxoid stroma. Nuclear polymorphism was evident; however, no mitotic abnormalities were found. Immunohistochemical staining revealed that the tumor was positive for vimentin and negative for p63, alpha-SMA, S100, CD21, STAT6, GFAP, and caldesmon. EWS-FISH revealed a clear separation of signals within the tumor, demonstrating the presence of an EWSR1 gene rearrangement. EWSR1-CREB1 gene fusion was not confirmed since we did not perform specific gene fusion transcripts using RT-PCR. Therefore, the tumor was diagnosed as PPMS with EWSR1 rearrangement. Four years have passed since surgery, and no apparent recurrence or metastasis has been detected in the patient.

      Conclusion

      PPMS is a rare low-grade sarcoma with distinct histological and genetic features. Due to the limited number of cases, the clinical behavior and prognosis of this disease is still unclear. To the best of our knowledge, only three patients have been reported in the literature to date to have developed metastasis during the follow-up period, which ranged from 4 months to 15 years. Further investigation through the accumulation of clinicopathological data on this rare disease is necessary for the identification of effective treatments and the features that predict the outcome of the disease.

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